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Leptin Resistance & Body-Weight Set-Point
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In one pass The more fat you carry, the less you ought to want to eat. Not this — Just push through the hunger and it'll fade — Hunger does not simply fade: one year after losing 10 kg, the hunger hormone ghrelin was still high and the fullness hormones PYY and leptin were still low — the body's defensive hunger does not reset (Sumithran 2011, NEJM).
Educational content, not medical advice — consult a clinician.
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Chapter 1
Leptin · adipose-to-brain energy signal
The more fat you carry, the less you ought to want to eat. The signal that says enough on the body's behalf is leptin, which fat cells release into the blood: the bigger the stores, the more they release. The hypothalamus, the appetite region at the base of the brain, picks it up, switches on the neurons that make you not want to eat, and holds down the ones that make you hungry.
It is not the brief fullness after a meal. It is a long-term fuel gauge for your reserves. When reserves are ample, the brain relaxes and lets metabolism and reproduction run normally. When they are low, it sounds a famine alarm: appetite grows and resting metabolism is turned down. Yet high leptin does not actively push you to eat less.
This one-sided setup, tight at one end and loose at the other, is one of the main reasons weight tends to come back after a diet. It also explains why extra leptin never became a weight-loss drug for ordinary obesity: what those people lack is not leptin.
It is not the brief fullness after a meal. It is a long-term fuel gauge for your reserves. When reserves are ample, the brain relaxes and lets metabolism and reproduction run normally. When they are low, it sounds a famine alarm: appetite grows and resting metabolism is turned down. Yet high leptin does not actively push you to eat less.
This one-sided setup, tight at one end and loose at the other, is one of the main reasons weight tends to come back after a diet. It also explains why extra leptin never became a weight-loss drug for ordinary obesity: what those people lack is not leptin.
Mechanism · leptin is the long-term fuel gauge
Leptin was discovered in 1994 by Friedman's lab, and it rewrote fat from a passive warehouse into an endocrine organ that secretes hormones.Here is how the circuit is wired. Fat cells release leptin continuously, in proportion to fat mass. Leptin travels in the blood, crosses the blood-brain barrier, and reaches a small area of the hypothalamus called the arcuate nucleus. There, two groups of neurons pull in opposite directions:
POMC neurons, which make you not want to eat: leptin activates them, and they release a signaling molecule called α-MSH that suppresses appetite.NPY/AgRP neurons, which make you hungry: leptin holds them down, so the drive to eat weakens.
One distinction matters. Leptin is not the kind of fullness signal that appears after a meal and fades soon after; that is the job of other gut hormones (CCK, PYY, ). Leptin reports the long-term reserves. When reserves are low and leptin falls, the brain not only urges you to eat but also turns down reproductive and thyroid hormones.
The strongest human evidence comes from an extremely rare group of children who cannot make leptin at all (a mutation in the ob gene). They feel hungry all the time and become severely obese, and injections of recombinant leptin dramatically reverse their obesity (Farooqi 1999 NEJM). For a while the whole field believed it had found a weight-loss drug. But people with ordinary obesity are not short of leptin, and that hope later fell through.
In evolutionary terms, leptin's job is not to keep you lean but to keep you from starving: it sounds the alarm hard when low, yet does not actively push you to eat less when high. Every defense after weight loss described in this story grows out of that asymmetry.
Myth · Can extra leptin make you lose weight?
The reasoning sounds smooth: if leptin is the signal that tells the brain to stop eating, why not give people with obesity a little more? It rests on a hidden assumption, that people are obese because they lack leptin. The truth is the reverse. More fat secretes more leptin, so blood leptin in people with obesity is clearly higher than in lean people. Their problem is not a shortage; it is that the brain's end cannot hear it (leptin resistance; see the chapter Leptin resistance · high leptin yet still hungry).The real test was Heymsfield 1999 JAMA, a randomized, double-blind, placebo-controlled trial with step-by-step dose increases. In it, 73 adults with ordinary obesity (none with a genetic leptin deficiency) injected recombinant leptin or placebo under the skin every day, all while following a diet about 500 kcal a day below their needs, for 24 weeks.
The trial itself was not pessimistic: the higher the dose, the more weight people lost on average, and that dose trend was statistically significant. At 24 weeks, mean weight change from baseline ranged from -0.7 (5.4) kg in the 0.01 mg/kg group (n=6) to -7.1 (8.5) kg in the 0.30 mg/kg group (n=8). Injection-site reactions were mostly mild to moderate, and no clinically meaningful adverse effects were seen in major organs.
But two details gave it away. First, individual variation was huge: the top-dose group had only 8 people, and its standard deviation was larger than its mean. Second, baseline leptin levels were unrelated to how much weight people lost. Recombinant leptin did not fail to become a drug for ordinary obesity because this one trial ruled it out; it failed because later research could not reproduce the effect and turn it into a dependable treatment.
This leaves two lessons you can take with you:
A hormone is not better when higher, or better when lower: what decides the outcome is whether the signal is received. Topping up a signal that is already in excess and unheard is unlikely to work.Dramatic benefit is limited to people with congenital leptin deficiency: a handful of families worldwide, under 0.01% of clinical obesity. Stretching their response to ordinary obesity is exactly where this myth comes from.
It also explains why the weight-loss drugs that later worked (the class) took a different route: instead of topping up the unheard signal, they press directly on the satiety circuit further downstream.
Chapter 2
Leptin resistance · high leptin yet still hungry
People with obesity often have more leptin in their blood, so by rights they should have no appetite, yet they still feel hungry. This is called leptin resistance: plenty of signal, but the hypothalamus cannot hear it clearly. Low-grade inflammation, less leptin transported into the brain, and a downstream pathway turned down give it the same shape as insulin resistance. The problem is not a shortage; it is noise drowning out the signal.
So adding more leptin does almost nothing in ordinary obesity. What you can do is cut the noise: regular exercise and losing visceral fat to lower inflammation, enough sleep, and fewer sugary drinks. This turns the signal up slowly, over months; it is not a one-click reset.
So adding more leptin does almost nothing in ordinary obesity. What you can do is cut the noise: regular exercise and losing visceral fat to lower inflammation, enough sleep, and fewer sugary drinks. This turns the signal up slowly, over months; it is not a one-click reset.
Mechanism · the signal is there; the brain cannot hear it
People with obesity have clearly higher blood leptin than lean people (more fat means more leptin). By the logic of the circuit they should have almost no appetite, yet in reality they feel as hungry as lean people, often hungrier.This is leptin resistance, and it has the same shape as insulin resistance: the hormone level is high, but the target cells do not respond.
Where does the signal get turned down? The main proposed steps are these:
SOCS3 goes up: a protein that suppresses cytokine signaling. The low-grade inflammation that comes with obesity raises it, and it blocks the JAK2/STAT3 pathway downstream of the leptin receptor (LepR), so the receptor receives the signal but the cell cannot pass it on.PTP1B and TCPTP: two phosphatases that strip phosphate groups off STAT3, cutting the signal off.Hypothalamic inflammation: in animals on a high-fat diet, the brain's immune cells (microglia) are activated and release inflammatory factors such as and , which damage neurons.Less transport across the blood-brain barrier: long-term high leptin reduces the transporters that carry it into the brain, so however high it is in the blood, only a limited amount reaches the hypothalamus.Endoplasmic reticulum stress, high insulin, and high blood glucose: together, they dampen leptin signaling.
Know the limits of this list: most of these molecular steps were established one by one in animals and are still hard to measure directly in people. They explain how the signal could be turned down, but how much each step contributes in humans is not yet clear.
This is also why, when Heymsfield 1999 injected recombinant leptin into people with ordinary obesity, the result was nothing like the dramatic response in congenital deficiency (trial details in the chapter Leptin · adipose-to-brain energy signal): they already had high leptin; the problem was resistance, not deficiency.
What it means clinically:
Recombinant leptin has still not become an obesity drug; it is used only for congenital leptin deficiency and generalized lipodystrophy.Leptin is not better when low, and not better when high; the question is whether the signal is being read. drugs are thought to bypass this blocked circuit and act directly on the POMC-neuron side.
In practice · Can resistance improve?
If the problem is that the signal cannot be read rather than that there is not enough signal, can the brain be made to hear it again? Partly, yes. But the lever is not topping up the hormone; it is removing the noise that jams the signal.Upstream of leptin resistance sit low-grade inflammation in the hypothalamus and a cluster of metabolic stresses (high insulin, high blood glucose, excess fructose, short sleep). Improve those, and the signaling pathway may clear somewhat. Directions worth trying, each with evidence of different strength:
Lower low-grade inflammation: regular exercise plus a diet built mainly on whole foods. The evidence that exercise improves insulin signaling in the body is fairly strong in people; its effect on leptin signaling in the hypothalamus comes mainly from animal experiments.Sleep enough: in a sleep-restriction trial in healthy young men, shorter sleep lowered leptin and raised ghrelin (Spiegel 2004). Seven to nine hours is not a luxury; it is the groundwork for repairing the signal.Eat less fructose, and cut sugary drinks first: that excess fructose worsens leptin resistance has been seen mainly in animal experiments and has not been measured directly in people, but drinking fewer sugary drinks has other reasons behind it anyway.Lose visceral fat: fat is itself a source of inflammation. Losing weight lowers inflammation, which may partly ease the resistance, a positive loop (although weight loss itself triggers the leptin-drop defense, which is why it has to be slow and paired with keeping muscle).
Two expectations to manage:
This turns the signal up; it does not reset it: improvement is gradual, over months, not visible in a week.Do not track progress by blood leptin: blood leptin mostly reflects fat mass and does not directly tell you how sensitive the brain's end is. Waist size, energy, how long a meal keeps you full, and sleep quality show the direction better.
As for drugs: the class does not repair leptin resistance. It bypasses the blocked circuit and presses on the satiety circuit further downstream. For people who have done all they can with lifestyle and still struggle, it is currently the strongest option (see GLP-1 agonists).
Chapter 3
Why the brain pulls weight back up
Your brain works like a thermostat for body weight: it treats your current weight as the set point to defend, and once you start losing, it uses every means it has to pull you back. This observation was first called set-point theory (Keesey & Powley 1986). A later, more realistic revision is settling-point theory: body weight is not a welded-in target but a range laid down by genes, environment, and long-term behavior; it can drift upward slowly, yet is very hard to drag back down with a short diet. The two theories agree on one thing: the brain defends a body-weight level.
There is also a structural reason. In adulthood the number of fat cells is largely fixed, with only about 10% renewed each year (Spalding 2008). When you lose weight, fat cells mainly shrink rather than disappear; the cells remain, ready to be filled again.
This defense works on appetite and on energy use at the same time, and it lasts longer than most people expect.
There is also a structural reason. In adulthood the number of fat cells is largely fixed, with only about 10% renewed each year (Spalding 2008). When you lose weight, fat cells mainly shrink rather than disappear; the cells remain, ready to be filled again.
This defense works on appetite and on energy use at the same time, and it lasts longer than most people expect.
Evidence · How long the defense lasts
Sumithran 2011 NEJM is a widely cited follow-up study:50 participants with overweight or obesity and no diabetes lost an average of 13.5 kg on a 10-week very-low-calorie diet (~ 500 kcal/d).Nine appetite-related hormones and subjective hunger were measured before weight loss, at week 10, and at week 62.At week 62 (about a year after the weight loss), participants had regained 5.5 kg on average, but the hormones were still tilted toward hunger:Ghrelin was still about 20% higher, continuing to push you to eat.Leptin was still about 36% lower, continuing to report low reserves.PYY and CCK, two post-meal fullness hormones, were still low, and several others, insulin among them, had not returned to their pre-diet levels.Subjective hunger scores were still higher., measured at the same visits, showed no clear difference from before the diet after a year, so it cannot be counted among the hormones still sounding the alarm.Conclusion: the hormonal changes brought on by weight loss last at least 1 year; it is not "a few weeks and you're fine".
Fothergill 2016 Obesity followed contestants from a weight-loss reality show and pushed the finding to its extreme:
14 extreme losers (about 58 kg lost in 30 weeks) were measured again 6 years later.After adjusting for body composition and age, resting metabolic rate (RMR) was still about 500 kcal/d below the predicted value. Most had regained weight, but their metabolism had not recovered with it.This adaptive drop in heat production was proportional to the weight loss they were maintaining at the time, and it can last for years.Its limits: only 14 people, and extreme weight loss, so the numbers cannot be applied directly to ordinary dieters.
Rosenbaum 2010 review: when weight is held 10% below its starting point, 24-hour total energy expenditure falls by about 20-25%, more than the change in weight and body composition can explain, as if the brain were actively rationing. ⚠️ Resting metabolic rate is not the part squeezed hardest: of the drop beyond the prediction, resting expenditure accounts for only 10-15%, and the other 85-90% comes from non-resting expenditure, the energy spent in daily activity and exercise.
Where the defense strikes:
Appetite: ghrelin rises, the NPY/AgRP neurons in the hypothalamus that make you hungry become more active (this link comes mainly from animal studies), and food reward becomes more compelling.Energy use: resting metabolism falls, fidgeting and everyday movement (NEAT) decline, and the thyroid hormone and sympathetic nerve activity go down.Attention: small brain-imaging studies found that after weight loss, food pictures trigger stronger responses in brain areas tied to reward and emotion (the orbitofrontal cortex and amygdala).Reproduction and immunity step back: when the energy gap is large, periods may become irregular, testosterone may fall, and immune-cell activity may drop, as energy is saved for survival.
Why some people stay weight-stable for years: not because they lack these mechanisms, but because they sit at their current set point, where the defense has no reason to switch on. Disrupt the status quo, by losing or gaining fat, and the system wakes up.
Chapter 4
Hunger and fullness hormones
Leptin tracks your long-term reserves; whether you feel hungry day to day is up to a different, short-term set of hormones. Ghrelin, released by the stomach, is the only circulating hormone currently known to drive hunger. After a meal, cholecystokinin (CCK) arrives fast, peptide YY (PYY) arrives later, and handles both fullness and insulin release; together they deliver the that's enough signal to the brain at different times.
Weight loss scrambles this whole ecosystem: you want to eat more, eating satisfies less, and fullness fades sooner. High protein, soluble fiber, and eating slowly all give the fullness signals time to arrive.
Weight loss scrambles this whole ecosystem: you want to eat more, eating satisfies less, and fullness fades sooner. High protein, soluble fiber, and eating slowly all give the fullness signals time to arrive.
Mechanism · Ghrelin and the fullness hormones
Ghrelin, the only appetite-stimulating circulating hormone known so far:It is secreted by a type of endocrine cell in the upper stomach (X/A-like cells), rising before meals and falling after them.Cummings 2002 NEJM, a small study: after diet-induced weight loss, the area under the 24-hour ghrelin curve rose; in a separate group of 5 people who had gastric bypass surgery, ghrelin was markedly suppressed.Sumithran 2011: about a year after weight loss, ghrelin was still about 20% higher, pushing you back toward your former weight.
Three post-meal fullness hormones, which rise after eating and dampen appetite:
Cholecystokinin (CCK): secreted by the duodenum, peaking about 15 minutes after a meal. It reports that fat and protein have entered the small intestine, brings a sense of fullness, stimulates bile release, and slows stomach emptying.Peptide YY (PYY): secreted by L cells in the ileum and colon, peaking 1-2 hours after a meal. It handles delayed fullness, the feeling of being truly full that arrives a while after eating. (glucagon-like peptide-1): also from L cells, rising after meals. It brings fullness in the brain and, at the same time, prompts the pancreatic β cells to release insulin.
Weight loss scrambles this ecosystem (Sumithran 2011): ghrelin runs high, PYY and CCK run low, and the same meal sends a weaker fullness signal. The result is that you want to eat more, find meals less satisfying, and get hungry again sooner. GLP-1 in that study showed no clear difference from before the diet after a year, so the accurate statement is that some fullness hormones weaken, not all of them.
Why GLP-1 weight-loss drugs can turn this around:
Semaglutide is a GLP-1 receptor agonist; tirzepatide acts on both the GLP-1 and GIP receptors. At drug-level concentrations they keep the fullness signal switched on for long periods.They are thought to press directly on the POMC-neuron side of the arcuate nucleus, bypassing the part of the circuit blocked by leptin resistance.You can think of them as stretching the post-meal peak of fullness hormones artificially, so that it does not fade all day.For mechanism, efficacy, and costs, see GLP-1 agonists.
In practice · Work with hunger hormones, not against them
Once you understand the rhythm of ghrelin and the fullness hormones, you can stop white-knuckling it and arrange your meals along the grain of the hormones instead. A few points you can use directly:Fixed mealtimes: fixing when you eat, instead of grazing all day, gives your stomach and brain a timetable.Eat slowly, so fullness signals have time to arrive: CCK and PYY signals are often said to take about 15-20 minutes to travel from gut to brain. People who eat fast have often overeaten before the signal lands. Putting utensils down between bites, drinking water with the meal, and talking with others can buy stronger fullness from the same amount of food.Solids over liquids: sugary drinks and juice carry almost 0 protein and 0 fat, trigger only a weak CCK response, and their calories are far less filling than the same calories in solid food. Eating fruit whole rather than juicing it is a free upgrade in fullness.Build on protein and soluble fiber: in after-meal measurements, a protein-rich meal (25-40 g per meal) raises PYY and and lowers ghrelin. Soluble fiber (oats, legumes, chia seeds) feeds gut bacteria that make short-chain fatty acids, raising PYY and GLP-1 further. Together they deliver the same calories, fuller for longer.Sleep enough: in a crossover trial in healthy young men, two nights of short sleep raised ghrelin by 28%, lowered leptin by 18%, and raised subjective hunger by 24% (Spiegel 2004). That trial held calorie intake fixed, so it measured hormones and hunger ratings, not how much more people actually ate.
One expectation to lower: after weight loss, these hormones are pushed toward a famine mode (ghrelin high, some fullness signals weak), and according to Sumithran 2011 this lasts at least a year. So the tools above are not temporary tricks for the weight-loss phase; they are habits to keep running through maintenance. You are not waiting for hunger to go away; you are using structure to keep working with it.
If what really runs out of control is not hunger but wanting to eat when you are already full, that is the reward system driving, not the hunger system. For that thread, see Hedonic Eating.
Chapter 5
What it means · this isn't a willpower problem
Weight coming back after a diet is not a moral failure; it is biology. Being hungry all the time after a diet, finding meals unsatisfying, craving food at midnight, being unable to walk past a picture of food: these are a physical response produced together by higher ghrelin, lower leptin, lower PYY and CCK, and a more sensitive reward circuit in the brain. Sumithran 2011 found these hormonal changes lasting at least 1 year; Fothergill 2016, in 14 people who had lost weight to an extreme, found the drop in resting metabolism lasting 6 years. Failing is not you being weak; it is the brain running an anti-famine program.
So the weight-loss phase is not the hard part; maintenance is. The weight-loss phase (weeks 0-12) has novelty and numbers to watch. In maintenance (after week 12, often for life), the hormones all pull the other way, the numbers stop moving, and motivation fades. What matters is not how much you lose but how long you keep it off.
So the weight-loss phase is not the hard part; maintenance is. The weight-loss phase (weeks 0-12) has novelty and numbers to watch. In maintenance (after week 12, often for life), the hormones all pull the other way, the numbers stop moving, and motivation fades. What matters is not how much you lose but how long you keep it off.
In practice · What holds the weight off
Nutrition strategy should aim at maintenance, not only at the weight-loss phase. The levers below differ in how strong their evidence is:Enough protein (25-40 g per meal, 1.2-1.6 g/kg a day): after meals it raises PYY and and lowers ghrelin, and it also helps keep muscle, so resting metabolism drops less.More fiber, especially soluble fiber (oats, legumes, chia seeds, vegetables): gut bacteria ferment it into short-chain fatty acids, which prompt L cells to release PYY and GLP-1.Cut sugary drinks and eat less fructose: that excess fructose worsens leptin resistance comes mainly from animal experiments, but there are good reasons to drink fewer sugary drinks anyway.Eat less ultra-processed food: in Hall 2019, an inpatient crossover trial in an NIH metabolic ward, people were offered two diets matched for calories and macronutrients and could eat as much as they liked; on the ultra-processed diet they ate about 508 kcal more per day.Sleep 7-9 hours: in sleep-restriction experiments, sleeping under 6 hours is often followed the next day by higher ghrelin, lower leptin, and 200-400 kcal of extra intake. (That extra-intake figure comes from other sleep studies; Spiegel 2004 held calories fixed and did not measure overeating.)Strength training: it keeps muscle so resting metabolism drops less, and it improves insulin sensitivity, which indirectly helps leptin signaling.
GLP-1 weight-loss drugs do exactly this: they use a drug to restore the fullness signal that weight loss weakened.
Semaglutide and tirzepatide keep the fullness signal switched on at drug-level concentrations for long periods, and they are thought to bypass the part of the circuit blocked by leptin resistance.In the STEP and SURMOUNT trial series, weight loss ran 15-22%, beginning to approach bariatric surgery (the two have not been compared head to head in the same trial).This is not cheating. It is an acknowledgment that set-point defense is a real biological mechanism, and willpower alone rarely wins.The cost shows up when the drug stops: in the STEP 1 extension study, about two-thirds of the lost weight came back within a year of stopping. So it is more like a blood-pressure drug, long-term management of a chronic condition.For mechanism, efficacy, and costs, see GLP-1 agonists.
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Mechanism · Can the set point move down?
The set point is not destiny, but it moves slowly. Reasoning from set-point and settling-point theory:Over years, steadily improving diet quality, sleep, exercise, and inflammation may let the set point drift down slowly. This step is hard to measure directly; it is a theoretical inference.Fast, extreme dieting wins on paper in the short term, but the hormones strike back, weight returns, and the set point may even move up.Pace is what matters: a slow, steady plan you can keep for life beats a fast, extreme plan that lasts 3 months.
Related stories: for why resting metabolism drops after weight loss, see Adaptive Thermogenesis; for using drugs to bypass this defense, see agonists; for the overall framework of weight loss (do not watch only the number on the scale), see Weight Management · Foundations; for how fructose is handled in the liver, see Fructose vs Glucose Metabolism; for the full account of the Hall 2019 ultra-processed food trial, see Ultra-processed Foods.
Your brain is not here to help you lose weight; it is here to keep you from starving. Once you understand that, you no longer need to hate yourself for being hungry.
References · 8
- Heymsfield, S. B., Greenberg, A. S., Fujioka, K., Dixon, R. M., Kushner, R., Hunt, T., Lubina, J. A., Patane, J., Self, B., Hunt, P., & McCamish, M. (1999). Recombinant leptin for weight loss in obese and lean adults: A randomized, controlled, dose-escalation trial. JAMA, 282(16), 1568–1575. 10.1001/jama.282.16.1568
- Sumithran, P., Prendergast, L. A., Delbridge, E., Purcell, K., Shulkes, A., Kriketos, A., & Proietto, J. (2011). Long-term persistence of hormonal adaptations to weight loss. The New England Journal of Medicine, 365(17), 1597–1604. 50 overweight or obese adults without diabetes on a 10-week very-low-energy diet; mean loss 13.5 kg. Measured at baseline, 10 and 62 weeks: leptin, ghrelin, PYY, GIP, GLP-1, amylin, pancreatic polypeptide, CCK, insulin and subjective appetite. At 62 weeks, leptin, PYY, CCK, insulin, ghrelin, GIP, pancreatic polypeptide and hunger still differed significantly from baseline; GLP-1 and amylin are not in that list. No thyroid hormone or energy-expenditure measure is reported in the abstract (abstract, PMID 22029981). 10.1056/NEJMoa1105816
- Rosenbaum, M., & Leibel, R. L. (2010). Adaptive thermogenesis in humans. International Journal of Obesity, 34(Suppl 1), S47–S55. Narrative review. Maintaining a 10% or greater reduction in body weight is accompanied by an approximate 20-25% decline in 24-hour energy expenditure; this fall in weight-maintenance calories is 10-15% below what is predicted from the changes in fat and lean mass, so a formerly obese person needs ~300-400 fewer calories a day than a never-obese person of the same weight and composition. Non-resting energy expenditure accounts for as much as 85-90% of the decline below predicted values, and skeletal-muscle work efficiency at low exercise levels rises by about 20%. Circulating T3 shows 'small but statistically significant decreases' - the review gives no percentage. Short-term leptin given to weight-reduced subjects, restoring pre-weight-loss leptin levels, reverses the lower energy expenditure, thyroid hormone and sympathetic activity, the higher muscle efficiency and the increased energy intake. The abstract cites an over 80% recidivism rate after weight loss (abstract, PMID 20935667; full text, PMC3673773). 10.1038/ijo.2010.184
- Fothergill, E., Guo, J., Howard, L., Kerns, J. C., Knuth, N. D., Brychta, R., Chen, K. Y., Skarulis, M. C., Walter, M., Walter, P. J., & Hall, K. D. (2016). Persistent metabolic adaptation 6 years after 'The Biggest Loser' competition. Obesity, 24(8), 1612–1619. 14 of the 16 original 'Biggest Loser' competitors re-measured 6 years later (DXA, indirect calorimetry). End of the 30-week competition: weight -58.3 kg, resting metabolic rate (RMR) -610 kcal/day. At 6 years: 41.0 kg regained, RMR still 704 kcal/day below baseline, and metabolic adaptation (RMR residual after adjusting for body composition and age) -499 ± 207 kcal/day. Regain was not correlated with metabolic adaptation at the competition's end (r = -0.1, P = 0.75), but those maintaining more weight loss at 6 years had greater concurrent metabolic slowing (r = 0.59, P = 0.025); the authors call adaptation a proportional but incomplete response to contemporaneous efforts to reduce weight (abstract, PMID 27136388). 10.1002/oby.21538
- Spalding, K. L., Arner, E., Westermark, P. O., Bernard, S., Buchholz, B. A., Bergmann, O., Blomqvist, L., Hoffstedt, J., Näslund, E., Britton, T., Concha, H., Hassan, M., Rydén, M., Frisén, J., & Arner, P. (2008). Dynamics of fat cell turnover in humans. Nature, 453(7196), 783–787. 10.1038/nature06902
- Cummings, D. E., Weigle, D. S., Frayo, R. S., Breen, P. A., Ma, M. K., Dellinger, E. P., & Purnell, J. Q. (2002). Plasma ghrelin levels after diet-induced weight loss or gastric bypass surgery. The New England Journal of Medicine, 346(21), 1623–1630. 10.1056/NEJMoa012908
- Spiegel, K., Tasali, E., Penev, P., & Van Cauter, E. (2004). Brief communication: Sleep curtailment in healthy young men is associated with decreased leptin levels, elevated ghrelin levels, and increased hunger and appetite. Annals of Internal Medicine, 141(11), 846–850. 10.7326/0003-4819-141-11-200412070-00008
- Hall, K. D., Ayuketah, A., Brychta, R., Cai, H., Cassimatis, T., Chen, K. Y., et al. (2019). Ultra-processed diets cause excess calorie intake and weight gain: an inpatient randomized controlled trial of ad libitum food intake. Cell Metabolism, 30(1), 67-77.e3. 20 inpatients, 2 weeks per diet, crossover. Meal eating rate was greater on the ultra-processed diet by 17 +/- 1 kcal/min (7.4 +/- 0.9 g/min), p < 0.0001 - that is the between-diet difference; ratings of pleasantness and familiarity did not differ (full text, PMC7946062). Diets were matched for presented calories, energy density including beverages (1.024 vs 1.028 kcal/g), macronutrients, sugar, sodium and fiber (21.3 vs 20.7 g/1000 kcal, partly via fiber supplements added to ultra-processed meals); non-beverage energy density was 1.957 vs 1.057 kcal/g (~85% higher), which the authors say likely contributed. Intake was 508 +/- 106 kcal/day greater on the ultra-processed diet (full text, Table 1 and Results). 10.1016/j.cmet.2019.05.008