What does Sarcopenia do in the body?

Story

Sarcopenia · The Quiet Loss of Muscle

Last updated September 2026

In one pass Sarcopenia is the loss of three things at once: the amount of skeletal muscle, the force it can produce, and the everyday movements it can carry out.

Educational content, not medical advice — consult a clinician.

Chapter 1

Not just 'old skinny'

Sarcopenia is the loss of three things at once: the amount of skeletal muscle, the force it can produce, and the everyday movements it can carry out. Stairs get hard, bags will not lift, falls come more easily, and a broken bone is slow to recover. It is not simply "getting thin with age"; it is one of the most preventable causes of disability in later life.

Muscle is more than the tissue that holds you up. It has two other jobs. First, it is the body's largest destination for glucose: after a meal, most of the sugar in the blood is taken up by muscle and stored as glycogen or burned. Second, it is the body's reserve of amino acids: in severe illness, infection or surgery, the body draws raw material from it for repair. So when muscle shrinks, what gives way is not only strength but balance, blood-sugar control, and the reserve you draw on when you fall ill.

The weight of this lands in the second half of life. Whether you can walk on your own, get up on your own, and get back up after a fall depends heavily on how much muscle you keep now.

Clinical · What follows when muscle is lost

When muscle is lost, a chain of consequences tends to follow:

Falls and fractures: muscle can no longer hold the body steady, balance gets worse, and one fall can mean a hip fracture; about 20–30% of people die within a year of a hip fractureHarder blood-sugar control: with less muscle, the sugar from a meal has lost its largest destination, insulin resistance worsens, and the risk of type 2 diabetes and cardiovascular disease rises with itLess reserve for a serious illness: in severe illness or infection the body draws raw material from the muscle store; people with a smaller store recover less well and face a higher risk of deathLoss of independence: not managing stairs, not getting out of bed, not carrying the shopping — step by step toward needing someone's careLifespan: a pooling observational studies (Wang 2020) found that older adults with less muscle had higher all-cause mortality, roughly in step with how much less. This is an association: people with little muscle also tend to be sicker and less active, and studies of this kind cannot separate which of these is doing the harm

Numbers · How much muscle is lost each decade

Muscle is lost year by year. The figures below are common rough estimates; studies differ, and so do people:

Ages 20–30: muscle mass peaksFrom 30: 0.5–1% a year, more if you do not trainAges 50–60: the loss speeds up to 1–1.5% a yearAfter 70: it speeds up again to 2–3% a year, and strength falls faster than size, because fat seeps into the muscle and the junctions between nerve and muscle also wear downAfter menopause: estrogen falls and the loss speeds up (the estrogen step is covered in Perimenopause)When men reach the stage of slowly falling testosterone (late-onset hypogonadism, LOH): muscle slowly declines along with it (see Andropause)
Older adults in China carry one more burden from diet habits: a lifetime of being told to "eat light, eat less meat, eat more vegetables" leaves them short of protein. In 2020 older Chinese adults ate only about 0.7–0.9 g/kg on average, while the PROT-AGE consensus puts the amount for healthy older adults at 1.0–1.2 g/kg a day, and at 1.2–1.5 g/kg for those with chronic disease. This is likely one reason sarcopenia is common in China.

Clinical · How a doctor confirms it

A doctor confirms sarcopenia in roughly three steps. The cut-offs below follow the Asian criteria (AWGS 2019); the European criteria (EWGSOP2) use the same logic with some different cut-offs:

Screen strength first: grip strength below 28 kg in men or 18 kg in women counts as weakThen measure muscle: dual-energy X-ray absorptiometry () or bioelectrical impedance (BIA) measures the muscle in the arms and legs, scaled to height squared; below 7.0 kg/m² in men or 5.4 kg/m² in women counts as lowCheck whether function is affected: walking too slowly (gait speed ≤ 0.8 m/s), or needing 11 seconds or more to stand up from a chair and sit back down 5 times
Prevalence climbs steeply with age (the Cruz-Jentoft 2019 review, plus surveys in China): about 14–19% of Chinese people over 65, higher in coastal regions; 20–30% over 70; and close to half over 80. Being a woman, older age, poor nutrition, sitting a lot and chronic disease push the risk highest when they come together.

Background · Where sarcopenia connects

Sarcopenia connects to several other stories on this site, and each connection is a piece of mechanism:

How muscle is built, and how leucine flips the switch for muscle building: Protein & Amino Acids and Muscle SystemHow vitamin D relates to muscle strength and falls: Vitamin DThe leucine metabolite that holds back muscle breakdown: β-Hydroxy-β-methylbutyrate ()The evidence for 5 g a day in older adults: Creatine monohydrateThe hormone thread (estrogen, testosterone): Perimenopause and Andropause
Why weight-loss drugs take muscle with them is covered in this story's chapter Protecting muscle on drugs.

Chapter 2

How much protein older adults need

You have probably seen the number: 0.8 g of protein per kg of body weight a day is enough (the US Recommended Dietary Allowance, ). It may be the most misread number in nutrition, and older adults and the people who cook for them misread it most often.

The cost of misreading it lands on muscle. With age, muscle responds less to protein: in a young adult a modest serving of protein flips the switch for muscle building, while the same amount in an older adult may not move it at all. This is called anabolic resistance. The key that turns the switch is leucine, an amino acid that directly starts muscle building: a young adult needs about 1 g to trigger it, while an older adult needs 25–40 g of protein in one meal, carrying 2.5–3 g of leucine, to push the switch over.

So for an older adult, protein is not only about how much is eaten in a day. It is about whether each meal crosses that threshold.

Myth · What the 0.8 figure actually measures

The 0.8 g/kg figure answers a narrow question: how little protein a healthy adult can eat before the body's protein starts running at a net loss. It is the Recommended Dietary Allowance the IOM set in 2005, defined as the intake that meets the needs of nearly all healthy people, and the nitrogen-balance studies behind it were done mostly in healthy young adults.

So hold on to three words: minimum, healthy, young. The figure answers "is it enough to avoid a deficit", not "how much is best", and it was not set with older age, or illness and recovery, in mind. Geriatric nutrition consensus groups such as PROT-AGE judged it too low for older adults, which is why they set a higher amount: 1.0–1.2 g/kg a day for older adults in good health.

iom-2005-macros

Mechanism · Why older bodies need more protein

Why does the same body need more protein once it is old? Three reasons twist together. The first is anabolic resistance: the same serving of protein has a harder time switching on muscle building in an older adult.

Second: part of what is eaten never reaches muscle. Older stomachs make less acid, so protein is digested less completely, and the gut moves and absorbs more slowly. Worse, a larger share of the amino acids that are absorbed is intercepted by the gut and liver for their own use — called splanchnic extraction — so less is left for the muscles of the arms and legs.

Third: older bodies already spend more protein. Age often brings a low-grade chronic inflammation, called inflammaging, in which the body quietly takes apart its own protein; chronic diseases keep asking for repair material; and an acute event such as pneumonia, a fall or surgery can push short-term need up to 2 g/kg a day.

Numbers · The daily amounts older adults need

Once you are older, real need sits a notch higher. These are the amounts from two geriatric nutrition consensus statements, PROT-AGE 2013 and ESPEN 2014 (both are expert consensus, built on an overall judgment of trials and metabolic studies):

Over 65 and in good health: 1.0–1.2 g/kg a dayOver 65 and exercising regularly: at least 1.2 g/kg a dayOver 65 with chronic disease, a recent acute illness, or already at nutritional risk: raise it to 1.2–1.5 g/kg a dayDuring a severe illness or marked malnutrition: up to 2.0 g/kg for a short periodOne important exception: people whose kidneys are already failing. PROT-AGE itself excludes people with an (the lab-sheet number that estimates kidney function) below 30 who are not yet on dialysis (chronic kidney disease, , stages 4–5). Under kidney-disease nutrition guidelines, protein is restricted — not raised — from CKD stage 3 onward, under the guidance of a nephrologist and a dietitian. How far is set by stage; the stage figures are in Renal System

Myth · Does more protein harm the kidneys?

"Older adults who eat more protein damage their kidneys" takes a conclusion that holds for people with kidney disease and stretches it to every older adult.

Separate the two groups:

People with normal kidney function ( above 60; eGFR is the lab-sheet number that estimates kidney function): a pooling trials in healthy adults (Devries 2018) found that kidney function changed no differently whether people ate more or less protein. On this evidence, higher intakes of up to about 2 g/kg a day showed no harm to kidney function (smaller studies such as Antonio 2016 point the same way)People who already have chronic kidney disease ( stages 3–5, eGFR below 60): protein is managed by stage. Before dialysis it usually has to be restricted; once dialysis starts, need rises, because dialysis removes protein. How much exactly is set by stage with a nephrologist and a dietitian; the stage figures are in Renal System
Where the misconception came from: trials in people with chronic kidney disease in the 1980–90s suggested that restricting protein might slow the loss of kidney function. That conclusion was later stretched to older adults with healthy kidneys, and for a healthy kidney the current evidence does not support "protein damages the kidneys".

In practice:

If you do not know your kidney function: over 65, check eGFR and urine albumin once before raising proteineGFR above 60: eat the full geriatric-consensus amount without worry (1.0–1.2 g/kg if in good health, 1.2–1.5 with chronic disease)eGFR below 60: see a nephrologist and a dietitian, and set it individually by stage
The common kidney harms are other things: long-term use of non-steroidal anti-inflammatory drugs (, such as ibuprofen or naproxen), diabetes and high blood pressure left uncontrolled for years, and some herbal products that contain aristolochic acid.

devries-2018-protein-kidney

In practice · Spreading protein across meals

One thing is easy to miss: it is not only how much, but how it is split. Since each meal has to cross the threshold on its own, the mechanism predicts that 25–40 g at each of three meals should beat scraping through the day and then eating 80 g in one go at night; however much you eat at dinner cannot make up for the two meals that fell short.

One very small crossover trial supports this direction (Mamerow 2014): the same healthy middle-aged volunteers ate two diets with the same total protein but a different split, and muscle protein synthesis over the whole day was higher when protein was spread evenly across three meals than when it was concentrated at dinner. It measured the rate of synthesis, not muscle mass or strength, and the volunteers were not older adults, so it supports the direction only.

At the table:

Aim for 25–40 g of protein at each meal (with at least 2.5 g of leucine); that, not "eating less meat", is what older adults should be doingWatch breakfast most closely: many older people start the day with a bowl of rice porridge and a steamed bun, only 5–10 g of protein, far shortA scoop of whey protein (15–25 g) is the easiest top-up, but it is a helping hand for a meal, not a replacement for one

mamerow-2014-protein-distribution

In practice · Which foods carry the leucine

Leucine content varies a lot from food to food. A rough picture is enough:

One egg: about 0.5 g100 g of chicken breast or 100 g of beef: about 2.5 g each100 g of salmon: about 1.5 g50 g of dry soybeans: about 2.0 gOne scoop of whey protein (25 g): 2.5–3 g, concentrated, and especially useful for older adults100 g of cooked rice: only 0.2 g, far from the threshold
How to rank protein sources, roughly: whey, eggs, fish, lean meat and chicken come first (high in leucine and easy to digest); then dairy such as yogurt and milk; then soy and tofu. Eating grains and beans together fills out the set of amino acids.

Chapter 3

Why strength training works best

If sarcopenia leaves you with one thing to remember, it is this: strength training is the first-line approach, and its effect is larger than any supplement's. In randomized trials, nutritional supplements alone, without training, barely moved muscle strength; training is what moved it.

Here is what happens in the body when you lift. The load puts a mechanical pull on the muscle, and that stress wakes a group of reserve cells beside the muscle fibers, called satellite cells, which merge into the fibers and thicken them. At the same time, connections between nerve and muscle that have worn down with age are rewired; part of the fast strength loss in older adults is a problem at the nerve end, not only in the muscle. Fat that has seeped into the muscle (myosteatosis) also decreases, and during a session testosterone, growth hormone and a growth-promoting signal molecule called insulin-like growth factor 1 () rise briefly.

Evidence · Can frail people in their 80s get stronger?

Behind the claim that strength training beats supplements sits a that has been cited for decades.

The Fiatarone study, published in the New England Journal of Medicine in 1994, enrolled 100 nursing-home residents who were already frail, with an average age of 87. They were randomly assigned to four groups for 10 weeks: strength training only, a nutritional supplement only, both, or neither. The training was high-intensity, mostly for the legs, at 80% of each person's one-repetition maximum (80% ; 1RM is the heaviest weight you can lift once).

After 10 weeks, muscle strength rose by an average of 113% in the people who trained, while it barely changed in those who did not; walking speed rose 12% and stair-climbing power 28%. And the group that took the supplement without training improved on none of the main outcomes.

The trial shows two things. First, people in their late eighties can still build strength — that is not just a comforting phrase. Second, older muscle still grows stronger with training, only more slowly; what matters is starting today, not having started young.

In practice · How heavy and how often

There is no need to memorize an exact dose. The general direction is this (the ACSM 2018 exercise-prescription guidelines, AHA 2024):

Frequency: 2–3 times a week, without training the same muscles two days in a rowEach major muscle group (legs, back and chest, shoulders, abdomen): 2–3 sets of 8–12 repetitionsIntensity: 60–80% of your maximum (60–80% , where 1RM is the heaviest weight you can lift once) is a safe range for older adults; aim for the feeling of having 1–2 repetitions left, but never managing a 5th moreProgression: add a little weight or a few repetitions every 2–4 weeks
You can train fully without a gym:

Standing up from a chair and sitting back down: arms crossed over the chest, 10 repetitions, 3 setsWall push-ups: pushing against a wall while standing, the older-adult version of a push-up; build up slowlyResistance bands: cheap, versatile and easy on older bodiesLight dumbbells (1–5 kg), or bottles filled with waterLeg raises and side leg raises: these train balance and the hips along the way

In practice · Cardio, food after training, safety

Walking alone is not enough. 150 minutes a week of moderate aerobic exercise (brisk walking, easy jogging) plus strength training 2–3 times a week is the pairing most often recommended for healthy aging; the intensity of a stroll does not stop muscle loss. When it comes to preventing sarcopenia, strength training does far more than aerobic exercise.

Feed the session afterward. 25–40 g of protein with leucine in the 2–3 hours after training pushes muscle building closer to its maximum; a common pattern for older adults is a scoop of whey after training, followed by a proper meal, on a base of enough calories, vitamin D and magnesium. Protein and training work best together (the Phillips 2017 review): protein without training adds very little strength; training without extra protein adds strength clearly; both together work best. The Fiatarone 1994 nursing-home trial points the same way: the group that took a supplement without training did not improve on the main outcomes.

On safety, watch for a few situations. People who have had a fall, or who have severe osteoarthritis (OA), should plan with a rehabilitation or geriatric doctor first. People with stable cardiovascular disease are safe at low to moderate intensity, but need an assessment before going to high intensity. For a steadier approach, balance training such as tai chi or yoga combined with strength training is one of the best combinations for preventing falls.

Watch the mechanism

Chapter 4

Protecting muscle on GLP-1 drugs

The past few years have brought a problem that older adults never had to think about: weight-loss injections. Drugs such as semaglutide and tirzepatide mimic a gut hormone called , and they bring the scale down fast — but not everything that comes off is fat; a large share is muscle.

Why does muscle go too? The main thing these drugs do is suppress appetite. People eat less, so they also eat less protein, and meals clear the muscle-building threshold less often. On top of that, any fast weight loss takes muscle with it — not only on these injections, but with every rapid method — and older adults already respond weakly to protein. Put together, the problem is magnified.

Hence the muscle-centric approach: the injection should not be used on its own, but tied to eating enough protein and doing strength training.

Numbers · How much of the weight lost is muscle

Over one to two years (12–24 months) these drugs can take off 15–20% of body weight. The catch is that 25–40% of what comes off is lean mass such as muscle (lean mass means all tissue other than fat, and muscle is a large part of it; the STEP-1 trial (Wilding 2021) and later analyses saw figures of this size). For an older adult already heading toward sarcopenia, adding this drug is like pressing the accelerator on the loss, and the risk of falls and fractures may rise with it.

The trap is not unique to the injections: any crash diet that brings the scale down fast takes muscle with it, and older adults cope worst. A very-low-calorie plan (VLCD) like the one used in the DiRECT trial calls for extra caution at this age.

In practice · Protecting muscle on a GLP-1 drug

What muscle-centric means in practice (the Lyon 2025 ACSM consensus):

Raise protein while on the drug; the consensus target is 1.6–2.0 g/kg a day. This comes with a hard condition: it holds only if kidney function is still normal ( ≥ 60 mL/min/1.73m²). People who already have chronic kidney disease () stages 3a–5 go the other way: protein is lowered step by step according to kidney function, under a nephrologist's guidance, with a focus on high-quality protein. How far it comes down is set by stage with a nephrologist and a dietitian (the stage figures are in Renal System); do not decide this on your ownDo strength training 2–3 times a weekDo not watch only the scale: a lower number does not mean the loss was fat; a scan or a body-composition analyzer (BIA) shows whether muscle has actually been lost

In practice · How an older adult should lose weight

How should an older adult, or a middle-aged person already at risk of sarcopenia, lose weight? The general direction is slowly: 0.5–1 kg a month is enough; do not chase 1 kg a week. Protein should not shrink along with portion sizes — keep to the PROT-AGE amounts as a floor (at least 1.2 g/kg a day for older adults who exercise regularly, 1.2–1.5 g/kg with chronic disease). Do strength training 2–3 times a week, and have a scan every 3–6 months to see what happened to muscle and fat separately. If a weight-loss injection is really needed, use it under a doctor's supervision rather than buying it and injecting yourself; it is not an over-the-counter (OTC) drug.

There is a distinction many people miss here: losing fat is not the same as losing weight. The scale measures a stew of water, muscle and fat all mixed together. What you should actually watch is body composition (DXA, BIA, waist circumference): fat going down while muscle stays. Losing fat, gaining a little muscle and barely changing weight is the healthy target — do not let the number on the scale fool you.

Evidence · Whey, creatine and HMB

When it comes to supplements, only a few have reasonable evidence:

Whey protein, 20–25 g a meal: the highest leucine density, easy to digest and quickly absorbed; it goes alongside a meal, not in place of oneCreatine, 5 g a day: combined with strength training, older adults gain somewhat more muscle and strength; the brain may benefit too, but the evidence for that is weaker (the Forbes 2023 and Candow 2014 ). It costs about $0.10 a day, which is very cheap (details in Creatine monohydrate) (β-hydroxy-β-methylbutyrate, a metabolite of leucine), 3 g a day: its strength is holding back muscle breakdown, not pushing muscle building. In one small randomized trial, older adults on strict bed rest for 10 days lost less lean mass if they took HMB (Deutz 2013); a meta-analysis pooling randomized trials across clinical populations (Bear 2019) found modest gains in muscle mass and strength, but the effects were small and the included studies carried a real risk of bias. So it suits acute illness, bed rest and undernutrition as an add-on, not as the main tool (details in β-Hydroxy-β-methylbutyrate (HMB))

Evidence · Vitamin D, magnesium and zinc

Vitamin D: people low in vitamin D (a blood level below 20 ng/mL, that is 50 nmol/L) are more prone to sarcopenia, and taking 800–2000 a day to close the gap may help strength a little. On falls, the Bischoff-Ferrari 2009 saw a benefit at the time, but later large trials showed that older adults who were not low in vitamin D to begin with did not fall less when they took more (covered in detail in Vitamin D)Magnesium and zinc: older adults often take in too little; getting enough supports the mitochondria and muscle building. This follows from the mechanism; few trials have tested it in sarcopenia specifically

bischoff-ferrari-2009-bmj-falls

Safety · Products to leave alone

A few things deserve cold water. For "miracle pill for seniors" marketing blends, take them apart and read each ingredient first. DHEA and testosterone products bought without a prescription carry real risks; a doctor has to assess you before you touch them. As for growth hormone, the US FDA does not allow it to be used as an anti-aging drug, and there are concerns that it may promote tumor growth — leave it alone.

Chapter 5

What to do at each age

There is no one-size-fits-all answer to preventing or treating sarcopenia; it depends on how old you are, because the place to push hardest differs from one stage of life to the next.

The most important point first: sarcopenia is not "the fate of getting old". It is a decline that starts around age 30 and can be prevented early. Whether at 80 you can climb stairs, carry the shopping and live independently depends heavily on whether you are doing strength training and eating enough protein today. Starting now is not too late, but every year of waiting makes it a little later.

The practical steps are laid out by age, together with checks you can do at home, advice for before and after illness or surgery, the most common mistakes older adults make, and one diagnosis that is often missed: sarcopenic obesity.

In practice · Building the reserve in youth and midlife

Ages 20–30: this is peak muscle mass, and what you build up now is worth the most. Eat 1.2–1.6 g/kg of protein a day, do strength training 2–3 times a week, and get enough calories and sleep. These habits will stay with you for 60 years; how much muscle you still have at 80 rests largely on the foundation laid in these years.

Ages 30–50: from here on, muscle is already quietly declining by 0.5–1% a year. Keep protein at 1.2–1.5 g/kg a day, and strength training stops being optional — yet many people in their thirties and forties do only aerobic exercise and never touch weights. Also avoid long hours of sitting, and look after core stability and balance.

In practice · Prevention and treatment after 50

Ages 50–65: this is the acceleration stage, where menopause in women and the slow decline of testosterone in men both fall. Keep protein at no less than 1.2–1.5 g/kg a day, do strength training 2–3 times a week, and have a scan or body-composition analysis (BIA) once a year to track the annual change in muscle; check vitamin D, magnesium and zinc at the same time.

Over 65 (the stage where prevention and treatment overlap): screen first. Grip strength, walking speed and standing up from a chair can all be tested at home: grip of at least 28 kg for men and 18 kg for women, and 5 chair stands within 11 seconds; if you fall short, see a doctor. Eat at least 1.2 g/kg of protein a day — the PROT-AGE amount for older adults who exercise regularly — rising to 1.2–1.5 g/kg with an acute or chronic illness, with 25–40 g at each meal. Do strength training 2–3 times a week in a version suited to older adults; take 800–2000 of vitamin D a day, plus sunlight; whey, creatine and can be used as add-ons; have a full assessment once a year, and take steps to prevent falls.

Clinical · After a diagnosis, and checks at home

If you have already been diagnosed with sarcopenia: see a geriatric or rehabilitation specialist, and step up nutrition and training together. at 3 g a day can serve as an add-on at this stage. Pause weight-loss injections and dieting, or assess them very carefully, and recheck after 6 months. The good news is that many people can turn this around.

At any age, a few movements make a home check; if you fall short, pay attention:

Sitting in a chair without using your hands, can you stand up and sit down 5 times in a row within 11 seconds?Can you walk 10 meters in under 12 seconds? (that works out to a walking speed of 0.8 m/s)Grip strength: at least 28 kg for men and 18 kg for women (Asian cut-offs; a grip dynamometer is easy to buy online)Can you climb 4 flights of stairs in one go without getting out of breath?
These are screening checks, not a diagnosis: falling short means it is worth getting a formal assessment from a doctor.

Clinical · Illness, surgery and bed rest

A few situations need extra care.

One is before an acute illness or surgery. If there is time, step up protein for 2 weeks beforehand (to 1.5–2 g/kg a day) and have and whey ready; after surgery, the sooner you are out of bed and into rehabilitation, the better. Older adults lose muscle quickly in bed; a commonly quoted figure is that one week of bed rest can cost 10–15%.

Another is a serious chronic disease such as cancer, chronic heart failure, chronic lung disease or chronic kidney disease (). These need a dietitian, with protein, training and supplements planned together (with CKD, protein follows the nephrologist's advice). Watch here for a hidden diagnosis, sarcopenic obesity: low muscle and high fat at the same time, while body weight and body mass index () look normal.

The third is a stay in intensive care (ICU) or long-term bed rest: critically ill patients can lose 10–25% of their muscle in a week. Start passive and then active exercise as early as possible, and step up nutrition at the same time.

Myth · The usual mistakes in older adults

The most common mistakes older adults make, in one place:

"Old people should eat less meat": wrong — that presses the accelerator on sarcopenia"Protein hurts the kidneys": for people with normal kidney function there is no evidence that it does; check "Older adults cannot train": wrong — people in their eighties can still train (the Fiatarone 1994 nursing-home trial)"Walking is enough": it is not; without strength training, muscle keeps being lost"A supplement will do it": supplements on their own do very little; they need training and proper meals alongside"Lose weight first": wrong — older adults should secure their muscle first, then work on fat

Clinical · Why sarcopenic obesity gets missed

Sarcopenic obesity means low muscle and high body fat at the same time. It is often missed because body weight and body mass index () may look normal.

Why it is often missed

Someone can have a BMI of 23 with body fat of 40% (a woman) or 28% (a man): the BMI is in the normal range, but body composition has already gone wrongA bathroom scale cannot tell how much of you is muscle and how much is fatSome people look slim but carry a lot of fat around their organs — called TOFI (thin outside, fat inside): high visceral fat and low muscle, yet an even-looking buildStudies have found that at the same BMI, Asian people tend to carry a larger share of visceral fat than Europeans, so this blind spot is more common in Asian populations
How it is diagnosed

The 2022 consensus of the European Association for the Study of Obesity and ESPEN (EASO 2022) asks for three things together:

Low muscle mass: a low appendicular muscle index on a scan — common cut-offs are below 5.5 kg/m² in women and 7.0 kg/m² in men — or the equivalent measure by bioelectrical impedance (BIA)High body-fat percentage: common thresholds are above 35–40% in women and above 25–30% in menDeclining function: low grip strength and slow walking speed
The exact cut-offs differ a little between standards.

Why the consequences are heavier

Observational studies find higher risks than with either low muscle or obesity alone: higher cardiovascular risk (pressure from both sides); more type 2 diabetes, metabolic syndrome, and fatty liver disease — metabolic dysfunction-associated steatotic liver disease, (formerly NAFLD); more falls and fractures, from being both heavy and weak; around 1.5–2 times the risk of disability and early death compared with people without it; and poorer tolerance of surgery and chemotherapy. These are associations, and the figures come from different populations.

Who should watch for it

Women after menopause (over 50)People who have lost weight fast on weight-loss injections ( drugs) or a very-low-calorie diet: fat and muscle go togetherPeople with chronic disease who sit a lot and eat a lot of ultra-processed foodPeople over 70 whose BMI looks normal but who have barely exercised for years
Why it matters more in the era of weight-loss injections

The injections bring weight down fast, and about 25–40% of the weight lost is lean mass rather than fat. Without strength training, a good deal of muscle goes along with the fat: the body looks slimmer, while function and metabolic health may get worse.

How to check at home (without a DXA scan)

Grip strength, the time for 5 chair stands, and walking speed (same cut-offs as the home checks in this chapter)Waist divided by height of 0.5 or more: a sign of excess abdominal fat, which it reflects more accurately than BMIA bathroom scale with body-fat measurement (BIA): look at body-fat percentage, not only weight
Formal diagnosis: a DXA scan (which separates whole-body and limb muscle), or a professional-grade bioelectrical impedance analyzer.

Treatment, in order of priority

1. Strength training 2–3 times a week, with the load raised step by step: the single intervention with the largest effect
2. Enough protein: the amounts for each age in this chapter (at least 1.2 g/kg a day over 65), 25–40 g per meal, with 2.5 g of leucine
3. A gentle calorie deficit (300–500 kcal a day less), not crash dieting
4. Aerobic exercise, to help keep fat in check
5. Enough vitamin D, magnesium and zinc
6. No smoking, less alcohol, enough sleep
7. Manage chronic conditions (type 2 diabetes, high blood pressure, depression)

Not recommended

A very-low-calorie diet (under 800 kcal a day): speeds up muscle loss, and the rebound is often largerAerobic exercise only, with no strength training: muscle goes down along with fatMeal replacements and nutrition shakes as staple food: often short on protein and low in fiber
Losing weight and losing fat are not the same thing

Losing weight means the number on the scale goes down: muscle, fat and water all drop togetherLosing fat while keeping muscle means fat goes down while muscle holds: the scale moves slowly, but metabolism is healthier
The real goal is the second. Read weight, waist and body-fat percentage together, and do not be fooled by the single number called "weight".

References · 10

Cruz-Jentoft, A. J., & Sayer, A. A. (2019). Sarcopenia. The Lancet, 393(10191), 2636-2646. 10.1016/S0140-6736(19)31138-9
Bauer, J., Biolo, G., Cederholm, T., Cesari, M., Cruz-Jentoft, A. J., Morley, J. E., et al. (2013). Evidence-based recommendations for optimal dietary protein intake in older people: PROT-AGE Study Group. JAMDA, 14(8), 542-559. 10.1016/j.jamda.2013.05.021
Deutz, N. E., Bauer, J. M., Barazzoni, R., Biolo, G., Boirie, Y., Bosy-Westphal, A., et al. (2014). Protein intake and exercise for optimal muscle function with aging: ESPEN. Clinical Nutrition, 33(6), 929-936. 10.1016/j.clnu.2014.04.007
Fiatarone, M. A., O'Neill, E. F., Ryan, N. D., Clements, K. M., Solares, G. R., Nelson, M. E., et al. (1994). Exercise training and nutritional supplementation for physical frailty in very elderly people. New England Journal of Medicine, 330(25), 1769-1775. 100 frail nursing-home residents (63 women, 37 men; mean age 87, range 72-98), 10 weeks, 94% completed. Strength rose 113% with resistance training vs 3% without; gait velocity +11.8% vs -1.0%; stair-climbing power +28.4% vs +3.6%; thigh-muscle area +2.7% vs -1.8% (P = 0.11, not significant). The multi-nutrient supplement had no effect on any primary outcome (abstract, PMID 8190152). 10.1056/NEJM199406233302501
American College of Sports Medicine. (2018). ACSM's Guidelines for Exercise Testing and Prescription (10th ed.). Wolters Kluwer. www.acsm.org/education-resources/books/guidelines-exercise-testing-prescription
Phillips, S. M. (2017). Current concepts and unresolved questions in dietary protein requirements and supplements in adults. Frontiers in Nutrition, 4, 13. Includes critical appraisal of HMB / leucine metabolite supplementation — small added effect on top of adequate dietary protein in trained adults. 10.3389/fnut.2017.00013
Wilding, J. P. H., Batterham, R. L., Calanna, S., Davies, M., Van Gaal, L. F., Lingvay, I., et al. (2021). Once-weekly semaglutide in adults with overweight or obesity (STEP-1). New England Journal of Medicine, 384(11), 989-1002. 1961 adults with BMI >= 30 (or >= 27 with a weight-related condition) and no diabetes, randomized 2:1 to semaglutide 2.4 mg weekly or placebo, plus lifestyle intervention, for 68 weeks. Mean body-weight change -14.9% vs -2.4% (difference -12.4 percentage points); >= 15% loss in 50.5% vs 4.9%; -15.3 kg vs -2.6 kg; discontinuation for gastrointestinal events 4.5% vs 0.8%. Funded by Novo Nordisk (abstract, PMID 33567185). 10.1056/NEJMoa2032183
Bear, D. E., Langan, A., Dimidi, E., et al. (2019). β-Hydroxy-β-methylbutyrate and its impact on skeletal muscle mass and physical function in clinical practice: a systematic review and meta-analysis. The American Journal of Clinical Nutrition, 109(4), 1119-1132. 15 RCTs, 2,137 patients with conditions involving muscle loss, HMB alone or HMB-containing (mostly multi-ingredient) supplements. Muscle mass SMD 0.25 (-0.00 to 0.50; P = 0.05), strength SMD 0.31 (0.12-0.50); no effect on body weight or other outcomes. The authors call the effect sizes small, and no study had low risk of bias in all categories (abstract, PMID 30982854). 10.1093/ajcn/nqy373
Deutz, N. E. P., Pereira, S. L., Hays, N. P., et al. (2013). Effect of β-hydroxy-β-methylbutyrate (HMB) on lean body mass during 10 days of bed rest in older adults. Clinical Nutrition, 32(5), 704-712. 24 healthy older adults (20 women, 4 men) randomized, double-blind, to Ca-HMB 1.5 g twice daily (3 g/day) or placebo, 10 days of complete bed rest then 8 weeks of resistance-training rehabilitation. 19 were evaluable after bed rest (control 8, HMB 11; age 60-76). Lean body mass fell 2.05 ± 0.66 kg with placebo vs -0.17 ± 0.19 kg with HMB (after excluding one subject); between-group P = 0.02. No differences in functional parameters could be seen, which the authors attribute to sample size; they call for a larger trial (abstract, PMID 23514626). 10.1016/j.clnu.2013.02.011
Moore, D. R., Churchward-Venne, T. A., Witard, O., Breen, L., Burd, N. A., Tipton, K. D., & Phillips, S. M. (2015). Protein ingestion to stimulate myofibrillar protein synthesis requires greater relative protein intakes in healthy older versus younger men. Journal of Gerontology Series A: Biological Sciences and Medical Sciences, 70(1), 57-62. Retrospective breakpoint analysis of pooled dose-response data: myofibrillar protein synthesis plateaued after 0.24 g/kg body mass in younger men versus 0.40 g/kg in older men (0.25 vs 0.60 g/kg lean body mass), i.e. older men need a greater relative per-meal protein dose. 10.1093/gerona/glu103

Reading room/ConditionsReader