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Reference topic 13: The Thrifty Body

Appetite, fat storage and obesity: the thrifty body

ProbableEvidence grade: Probable. Good observational evidence with a plausible mechanism, or small or few trials.89 sources7 graded recommendationsTopic hub: Food

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In 1963 a National Institutes of Health (NIH) survey of arthritis among the Pima of the Gila River Indian Community, in southern Arizona, found something nobody had come looking for. It "unexpectedly revealed that many members of the community were diabetic," an NIH investigator later wrote.1 By the late 1970s a long-term NIH study had recorded the highest rate of new diabetes cases its authors knew of, 19 times the rate in Rochester, Minnesota. Among Pima adults over 35, 40 to 50% had the disease.2

It was new. As late as 1906 a review of Pima medical conditions listed a single case of diabetes.1 The change had begun with water. In the 1870s and 1880s, non-Native farmers upstream dammed and diverted the Gila, the river that watered the fields of the Akimel O'otham, the people the Spanish named Pima. Decades of famine followed. In the Community's own account, "The federal government stepped in and doled out canned and processed food by the ton."3 In time the diet came to draw "more than forty percent of its energy from fat."4

Mismatch card

The system

Energy storage and appetite: fat, the hormones that report on it, and the muscle, liver and pancreas that handle fuel.

What it expects

Food that takes work to get, lean seasons, fiber-rich plants and hours of physical work.

What it gets

Cheap, energy-dense, ultra-processed food all day, little physical work and short sleep.

What happens in the gap

Fat accumulates, a body built to defend its stores resists losing it, and fat that overflows into liver, muscle and pancreas is thought to drive insulin resistance and type 2 diabetes.

The handrail

Minimally processed food rich in fiber and protein, aerobic and strength training, enough sleep, and GLP-1 drugs with a clinician where appropriate (●●○)

Strength of evidence

●●○ Natural experiments and large drug and lifestyle trials are strong; the thrifty-gene story is weak, and diet composition is still debated.

What this topic covers

  • ·Maycoba Climbs the Stairs
  • ·The Gene That Was Supposed to Explain It
  • ·Islands of Plenty
  • ·Okinawa's Two Generations
  • ·The Constrained Engine
  • ·A Body Built to Defend
  • ·Where the Fat Goes
  • ·The Lizard's Gift

The practical version is in the book: Chapter 5, Eat.

The handrail

Topic 40 has the full program; these steps target the thrifty body.

Each recommendation carries the strength of the evidence behind it. How the grades work.

  1. Change the food around you, not your willpower

    ProbableEvidence grade: Probable. Good observational evidence with a plausible mechanism, or small or few trials.

    Make minimally processed food the easy default (Topic 11); across 25 populations, more ultra-processed food went with more body fat.36

  2. Aim for at least 25 g of fiber a day

    ProbableEvidence grade: Probable. Good observational evidence with a plausible mechanism, or small or few trials.

    from legumes, whole grains, vegetables and fruit, building up slowly. Benefits peaked at 25-29 g in meta-analyses, and more may help.84

  3. Eat enough protein

    ProbableEvidence grade: Probable. Good observational evidence with a plausible mechanism, or small or few trials.

    at least 0.8 g per kg of body weight a day, with 1.2-1.6 g/kg proposed during active weight loss, and not 2 g/kg or more for long periods.85 With kidney disease, ask a clinician before raising protein.

  4. Move for insulin sensitivity, not to burn off food

    StrongEvidence grade: Strong. Multiple randomized controlled trials, or consistent large cohort studies with a well-understood mechanism.

    Aim for 150-300 minutes a week of moderate activity plus resistance training on two or three non-consecutive days. A session can improve insulin sensitivity for 2 to 72 hours, so avoid more than two days off in a row.86 Light walking breaks during long sitting lower blood sugar after meals (●●○).87 If you take insulin or a sulfonylurea, watch for low blood sugar; with diabetes complications, ask for an adapted plan.8688

  5. Protect your sleep

    ProbableEvidence grade: Probable. Good observational evidence with a plausible mechanism, or small or few trials.

    If you habitually sleep under 6.5 hours, try to extend it. In 80 such adults with overweight, one sleep-hygiene session added about 1.2 hours a night and cut intake by about 270 kcal a day over two weeks.89

  6. Act early

    StrongEvidence grade: Strong. Multiple randomized controlled trials, or consistent large cohort studies with a well-understood mechanism.

    With prediabetes, a program aiming at 7% weight loss and 150 minutes of weekly activity cut diabetes incidence by 58% over about three years.90 With recent type 2 diabetes, ask about supervised diet-based remission, and never stop diabetes or blood-pressure drugs on your own.50

  7. Treat GLP-1 drugs as a legitimate medical option

    StrongEvidence grade: Strong. Multiple randomized controlled trials, or consistent large cohort studies with a well-understood mechanism.

    chosen with a clinician and planned as long-term treatment, since weight usually returns after stopping.68 The trials enrolled adults with a BMI of 30 or more (27 with a weight-related condition).65 Pair them with exercise, including strength training, and enough protein (●●○). In one trial, exercise plus the related drug liraglutide cut body-fat percentage about twice as much as either alone, and protein without strength training is unlikely to protect muscle.9185 Nausea and other gut side effects are common.65 Semaglutide's label rules it out for anyone with a personal or family history of medullary thyroid carcinoma or multiple endocrine neoplasia type 2. It also says to stop the drug at least two months before a planned pregnancy. Tell the surgical team before anesthesia, and report severe abdominal pain or sudden vision loss at once.8883 With a history of eating disorders, involve your specialist.

The skeptic's corner

The case against this topic, from the research itself.

Carbohydrates or calories? The carbohydrate-insulin model holds that high-glycemic diets, heavy in foods that raise blood sugar fast, trigger a hormonal response that drives fat storage and then overeating. Its authors include Daniel Lieberman, whose work runs through this book.72 The rival energy balance model answers that the brain is the main organ that regulates body weight.73 In a tightly controlled test at the NIH Clinical Center, 20 adults eating freely took in 689 kcal a day less on a low-fat plant-based diet than on a ketogenic (very low-carbohydrate) animal-based one.74 A feeding trial found higher energy spending on a low-carbohydrate diet, but critics fault its analysis.7576 In a year-long trial, healthy low-fat and healthy low-carbohydrate diets did about equally well.77

Thrifty genes survive in pieces. A few population-specific variants, such as the Samoan one, fit; the general theory does not, and drift is barely tested either.10

"Metabolic damage," the idea that dieting permanently breaks metabolism, overstates a real effect. The slowdown roughly tracks the effort of staying lighter, may fade once weight is stable, and in the eight-week diet study peaked at about 100 kcal a day.4041 Nor does metabolism sag in midlife: across thousands of people from infancy to old age, size-adjusted energy spending held steady from about 20 to 60.78

BMI is a blunt tool. A recent Lancet Commission recommended using it only to gauge risk across populations or to screen, not to judge one person's health. It also proposed separating "clinical" obesity, which harms organs or daily life, from "preclinical" obesity.79

The new drugs leave open questions. In a large US study, nearly two-thirds of people without diabetes who started one stopped within a year.80 Lean tissue makes up anywhere from 15% or less to 60% of the weight lost, though some of the muscle change may be adaptive.8182 Heart benefit has been shown over about three years, not decades.67 Europe's medicines regulator has concluded that NAION (a loss of blood flow to the optic nerve that can cost vision) is a very rare side effect of semaglutide, affecting up to 1 in 10,000 users.83 And more than half of US users said the drugs were difficult to afford.70

Terms this topic defines

Related topics

Sources cited above

  1. 1.Pratley, R.E. (1998). "Gene-environment interactions in the pathogenesis of type 2 diabetes mellitus: lessons learned from the Pima Indians." Proceedings of the Nutrition Society, 57(2), 175-181. https://doi.org/10.1079/PNS19980029
  2. 2.Knowler, W.C., Bennett, P.H., Hamman, R.F., and Miller, M. (1978). "Diabetes incidence and prevalence in Pima Indians: a 19-fold greater incidence than in Rochester, Minnesota." American Journal of Epidemiology, 108(6), 497-505. https://doi.org/10.1093/oxfordjournals.aje.a112648 (26.5 new cases per 1,000 person-years)
  3. 3.Gila River Indian Community (n.d.). History. https://www.gilariver.org/index.php/about/history (accessed 19 September 2026). (in the Community's account, the famine ran from 1880 "to 1920 or so")
  4. 4.Schulz, L.O., and Chaudhari, L.S. (2015). "High-risk populations: the Pimas of Arizona and Mexico." Current Obesity Reports, 4(1), 92-98. https://doi.org/10.1007/s13679-014-0132-9 (Maycoba diet in 1995: about 25% of calories from fat and more than 50 g of fiber a day; obesity among Arizona Pima: 64% of men and 75% of women; until 1991 the only way in was an arduous drive from Hermosillo that included a harrowing crossing of a rope bridge)
  5. 5.Ravussin, E., Valencia, M.E., Esparza, J., Bennett, P.H., et al. (1994). "Effects of a traditional lifestyle on obesity in Pima Indians." Diabetes Care, 17(9), 1067-1074. https://doi.org/10.2337/diacare.17.9.1067
  6. 72.Ludwig, D.S., Aronne, L.J., Astrup, A., de Cabo, R., et al. (2021). "The carbohydrate-insulin model: a physiological perspective on the obesity pandemic." American Journal of Clinical Nutrition, 114(6), 1873-1885. https://doi.org/10.1093/ajcn/nqab270 (17 authors)
  7. 73.Hall, K.D., Farooqi, I.S., Friedman, J.M., Klein, S., et al. (2022). "The energy balance model of obesity: beyond calories in, calories out." American Journal of Clinical Nutrition, 115(5), 1243-1254. https://doi.org/10.1093/ajcn/nqac031
  8. 74.Hall, K.D., Guo, J., Courville, A.B., Boring, J., et al. (2021). "Effect of a plant-based, low-fat diet versus an animal-based, ketogenic diet on ad libitum energy intake." Nature Medicine, 27(2), 344-353. https://doi.org/10.1038/s41591-020-01209-1
  9. 75.Ebbeling, C.B., Feldman, H.A., Klein, G.L., Wong, J.M.W., et al. (2018). "Effects of a low carbohydrate diet on energy expenditure during weight loss maintenance: randomized trial." BMJ, 363, k4583. https://doi.org/10.1136/bmj.k4583 (20-week trial; expenditure 209 kcal a day higher on the low-carbohydrate diet)
  10. 76.Hall, K.D., Guo, J., and Speakman, J.R. (2019). "Do low-carbohydrate diets increase energy expenditure?" International Journal of Obesity, 43(12), 2350-2354. https://doi.org/10.1038/s41366-019-0456-3
  11. 77.Gardner, C.D., Trepanowski, J.F., Del Gobbo, L.C., Hauser, M.E., et al. (2018). "Effect of low-fat vs low-carbohydrate diet on 12-month weight loss in overweight adults and the association with genotype pattern or insulin secretion." JAMA, 319(7), 667-679. https://doi.org/10.1001/jama.2018.0245 (DIETFITS). (609 adults)
  12. 10.Brassington, L., Arner, A.M., Watowich, M.M., Damstedt, J., et al. (2024). "Integrating the thrifty genotype and evolutionary mismatch hypotheses to understand variation in cardiometabolic disease risk." Evolution, Medicine, and Public Health, 12(1), 214-226. https://doi.org/10.1093/emph/eoae014
  13. 40.Fothergill, E., Guo, J., Howard, L., Kerns, J.C., et al. (2016). "Persistent metabolic adaptation 6 years after 'The Biggest Loser' competition." Obesity, 24(8), 1612-1619. https://doi.org/10.1002/oby.21538 (the 14 contestants had regained 41.0 of the 58.3 kg they had lost)
  14. 41.Martins, C., Roekenes, J., Salamati, S., Gower, B.A., et al. (2020). "Metabolic adaptation is an illusion, only present when participants are in negative energy balance." American Journal of Clinical Nutrition, 112(5), 1212-1218. https://doi.org/10.1093/ajcn/nqaa220 (the one-year result is for the 45 participants with complete data)
  15. 78.Pontzer, H., Yamada, Y., Sagayama, H., Ainslie, P.N., et al. (2021). "Daily energy expenditure through the human life course." Science, 373(6556), 808-812. https://doi.org/10.1126/science.abe5017 (6,421 people aged 8 days to 95 years)
  16. 79.Rubino, F., Cummings, D.E., Eckel, R.H., Cohen, R.V., et al. (2025). "Definition and diagnostic criteria of clinical obesity." Lancet Diabetes and Endocrinology, 13(3), 221-262. https://doi.org/10.1016/S2213-8587(24)00316-4
  17. 80.Rodriguez, P.J., Zhang, V., Gratzl, S., Do, D., et al. (2025). "Discontinuation and reinitiation of dual-labeled GLP-1 receptor agonists among US adults with overweight or obesity." JAMA Network Open, 8(1), e2457349. https://doi.org/10.1001/jamanetworkopen.2024.57349 (125,474 people starting a GLP-1 drug; 64.8% of those without diabetes stopped within a year)
  18. 81.Wilding, J.P.H., Batterham, R.L., Calanna, S., Van Gaal, L.F., et al. (2021). "Impact of semaglutide on body composition in adults with overweight or obesity: exploratory analysis of the STEP 1 study." Conference abstract, ENDO 2021. https://www.newswise.com/pdf_docs/16159288255831_Wilding%20Abstract.pdf (fat mass fell 19.3% and lean mass 9.7%)
  19. 82.Neeland, I.J., Linge, J., and Birkenfeld, A.L. (2024). "Changes in lean body mass with glucagon-like peptide-1-based therapies and mitigation strategies." Diabetes, Obesity and Metabolism, 26(Suppl 4), 16-27. https://doi.org/10.1111/dom.15728
  20. 67.Lincoff, A.M., Brown-Frandsen, K., Colhoun, H.M., Deanfield, J., et al. (2023). "Semaglutide and cardiovascular outcomes in obesity without diabetes." New England Journal of Medicine, 389(24), 2221-2232. https://doi.org/10.1056/NEJMoa2307563 (mean follow-up 39.8 months; hazard ratio 0.80). (20% lower risk)
  21. 83.European Medicines Agency (2025). "PRAC concludes eye condition NAION is a very rare side effect of semaglutide medicines Ozempic, Rybelsus and Wegovy." 6 June 2025. https://www.ema.europa.eu/en/news/prac-concludes-eye-condition-naion-very-rare-side-effect-semaglutide-medicines-ozempic-rybelsus-wegovy
  22. 70.KFF (2025). "Poll: 1 in 8 adults say they are currently taking a GLP-1 drug for weight loss, diabetes or another condition, even as half say the drugs are difficult to afford." 14 November 2025 (fieldwork 27 October-2 November 2025, n=1,350). https://www.kff.org/public-opinion/poll-1-in-8-adults-say-they-are-currently-taking-a-glp-1-drug-for-weight-loss-diabetes-or-another-condition-even-as-half-say-the-drugs-are-difficult-to-afford/ (12% currently taking a GLP-1 drug; 56% of users said the drugs were difficult to afford)
  23. 36.McGrosky, A., Luke, A., Arab, L., Bedu-Addo, K., et al. (2025). "Energy expenditure and obesity across the economic spectrum." Proceedings of the National Academy of Sciences, 122(29), e2420902122. https://doi.org/10.1073/pnas.2420902122 (4,213 adults; dietary data for 25 populations)
  24. 84.Reynolds, A., Mann, J., Cummings, J., Winter, N., et al. (2019). "Carbohydrate quality and human health: a series of systematic reviews and meta-analyses." The Lancet, 393(10170), 434-445. https://doi.org/10.1016/S0140-6736(18)31809-9
  25. 85.Mozaffarian, D., Agarwal, M., Aggarwal, M., Alexander, L., et al. (2025). "Nutritional priorities to support GLP-1 therapy for obesity: a joint Advisory from the American College of Lifestyle Medicine, the American Society for Nutrition, the Obesity Medicine Association, and The Obesity Society." Obesity, 33(8), 1475-1503. https://doi.org/10.1002/oby.24336 (published simultaneously in American Journal of Clinical Nutrition, 122(1), 344-367, https://doi.org/10.1016/j.ajcnut.2025.04.023).
  26. 86.Kanaley, J.A., Colberg, S.R., Corcoran, M.H., Malin, S.K., et al. (2022). "Exercise/physical activity in individuals with type 2 diabetes: a consensus statement from the American College of Sports Medicine." Medicine and Science in Sports and Exercise, 54(2), 353-368. https://doi.org/10.1249/MSS.0000000000002800
  27. 87.Buffey, A.J., Herring, M.P., Langley, C.K., Donnelly, A.E., et al. (2022). "The acute effects of interrupting prolonged sitting time in adults with standing and light-intensity walking on biomarkers of cardiometabolic health in adults: a systematic review and meta-analysis." Sports Medicine, 52(8), 1765-1787. https://doi.org/10.1007/s40279-022-01649-4
  28. 88.Novo Nordisk and U.S. Food and Drug Administration (2026). WEGOVY (semaglutide) injection and tablets: highlights of prescribing information, revised 02/2026. https://www.accessdata.fda.gov/drugsatfda_docs/label/2026/215256s033lbl.pdf
  29. 89.Tasali, E., Wroblewski, K., Kahn, E., Kilkus, J., et al. (2022). "Effect of sleep extension on objectively assessed energy intake among adults with overweight in real-life settings." JAMA Internal Medicine, 182(4), 365-374. https://doi.org/10.1001/jamainternmed.2021.8098
  30. 90.Knowler, W.C., Barrett-Connor, E., Fowler, S.E., Hamman, R.F., et al., for the Diabetes Prevention Program Research Group (2002). "Reduction in the incidence of type 2 diabetes with lifestyle intervention or metformin." New England Journal of Medicine, 346(6), 393-403. https://doi.org/10.1056/NEJMoa012512
  31. 50.Lean, M.E.J., Leslie, W.S., Barnes, A.C., Brosnahan, N., et al. (2018). "Primary care-led weight management for remission of type 2 diabetes (DiRECT): an open-label, cluster-randomised trial." The Lancet, 391(10120), 541-551. https://doi.org/10.1016/S0140-6736(17)33102-1 (assigned practice by practice; formula diet of 825-853 kcal a day)
  32. 68.Wilding, J.P.H., Batterham, R.L., Davies, M., Van Gaal, L.F., et al. (2022). "Weight regain and cardiometabolic effects after withdrawal of semaglutide: the STEP 1 trial extension." Diabetes, Obesity and Metabolism, 24(8), 1553-1564. https://doi.org/10.1111/dom.14725 (327 participants from both trial arms; all analyses exploratory). (extension of the 68-week trial; one year off treatment)
  33. 65.Wilding, J.P.H., Batterham, R.L., Calanna, S., Davies, M., et al. (2021). "Once-weekly semaglutide in adults with overweight or obesity." New England Journal of Medicine, 384(11), 989-1002. https://doi.org/10.1056/NEJMoa2032183
  34. 91.Lundgren, J.R., Janus, C., Jensen, S.B.K., Juhl, C.R., et al. (2021). "Healthy weight loss maintenance with exercise, liraglutide, or both combined." New England Journal of Medicine, 384(18), 1719-1730. https://doi.org/10.1056/NEJMoa2028198

This topic carries 89 notes in the research manuscript; the 34 above are those behind the material on this page. Full source register.