Should You Count Calories?

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Should you count calories? A century ago, a Los Angeles doctor named Lulu Hunt Peters sold two million copies of a book that taught American women to count calories as a patriotic duty during WWI. She invented the 100-calorie snack pack. She set the 1,200-calorie floor that still haunts diet apps in 2026. The framework she popularized is still running your relationship with food.

This week, Zoë and Kylee dig into the question every active person has wondered about: should you be counting calories? They trace how a unit of heat invented to measure factory worker rations became the dominant logic of American eating. Where the 2,000-calorie label on every food package actually came from (it isn't science, it's a 1990 design choice). Why calorie counting is legally allowed to be 20 percent wrong before it ever reaches your plate. And why a framework with this many cracks has held on for a hundred years.

Along the way: what calorie counting did to the American food supply during the low-fat era, what the Biggest Loser metabolic adaptation research actually showed, why even registered dietitians can't accurately track their own intake, what set point theory says about why restriction backfires, and whether calorie tracking apps are tools, traps, or both. For athletes, the questions that actually matter for performance, and what the research says about who calorie counting helps and who it harms.

Plus: the early feminist origins of dieting (yes, really), why your microbiome is doing math your app can't see, and why this number keeps its grip on us even when the science says it shouldn't.

Listen for the full story.

Episode Chapters +

• 00:00 — The MyFitnessPal era and how calorie tracking gets its hooks in
• 05:50 — What a calorie actually is: the bomb calorimeter and the Atwater system
• 11:00 — Wilbur Atwater, factory workers, and the origin of the calorie
• 13:30 — Lulu Hunt Peters and the 1918 book that built modern diet culture
• 16:20 — The flapper era, the bathroom scale, and dieting as patriotic duty
• 20:00 — Why the calorie became sticky: quantification, morality, and control
• 22:30 — The low-fat era catastrophe of the 1980s and 90s
• 25:30 — Why calories in / calories out is incomplete
• 28:00 — The Biggest Loser study and metabolic adaptation
• 31:00 — Set point theory and the Minnesota Starvation Experiment
• 38:00 — When a 22-year-old eating 1,820 calories couldn't lose weight
• 42:00 — The self-reporting problem: why nutrition research is built on sand
• 46:00 — Personal confessions: when tracking goes sideways
• 53:00 — Where the 2,000-calorie label actually came from (it isn't science)
• 57:00 — The 1,200-calorie floor and other extreme low-cal diets
• 58:30 — Menu labeling laws: what works, what backfires, who pays the price
• 1:03:00 — Tracking apps, gamification, and eating disorder risk
• 1:09:00 — Athletes, RED-S, and the danger of prescribed low-calorie diets
• 1:11:30 — Tool, trap, or both? The bottom line
• 1:13:00 — Why this framework still has a grip on us

Topics Covered +

• The history of calorie counting and where the framework came from
• Wilbur Atwater, bomb calorimetry, and how food energy is measured
• Lulu Hunt Peters and the 1918 invention of modern diet culture
• Why the 20% margin of error on calorie labels matters
• The 2,000-calorie daily value: a 1990 design choice, not a scientific standard
• The 1,200-calorie floor and where it actually comes from
• The low-fat era and the unintended consequences of calorie-focused policy
• Metabolic adaptation, the Biggest Loser study, and set point theory
• The Minnesota Starvation Experiment and what it taught us about restriction
• Self-reporting error in nutrition research (and why even RDs underreport)
• Doubly labeled water and the gold standard for measuring intake
• Menu calorie labeling: research on behavior change and unintended harm
• Calorie tracking apps, gamification mechanics, and eating disorder risk
• RED-S, low energy availability, and the danger of prescribed restriction in athletes
• Why "energy balance" isn't the whole story
• What calorie counting can actually be useful for (and who it harms)

Studies & References +

Atwater, W. O. (1894). Foods: Nutritive value and cost. USDA Farmers' Bulletin No. 23. U.S. Department of Agriculture.

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.

Keys, A., Brožek, J., Henschel, A., Mickelsen, O., & Taylor, H. L. (1950). The biology of human starvation (Vols. 1–2). University of Minnesota Press.

Lichtman, S. W., Pisarska, K., Berman, E. R., Pestone, M., Dowling, H., Offenbacher, E., Weisel, H., Heshka, S., Matthews, D. E., & Heymsfield, S. B. (1992). Discrepancy between self-reported and actual caloric intake and exercise in obese subjects. New England Journal of Medicine, 327(27), 1893–1898.

National Academies of Sciences, Engineering, and Medicine. (2023). Dietary Reference Intakes for Energy. National Academies Press.

Champagne, C. M., Bray, G. A., Kurtz, A. A., Monteiro, J. B. R., Tucker, E., Volaufova, J., & DeLany, J. P. (2002). Energy intake and energy expenditure: A controlled study comparing dietitians and non-dietitians. Journal of the American Dietetic Association, 102(10), 1428–1432.

Peters, L. H. (1918). Diet and health, with key to the calories. Reilly & Lee.

Linardon, J., & Messer, M. (2019). My fitness pal usage in men: Associations with eating disorder symptoms and psychosocial impairment. Eating Behaviors, 33, 13–17.

Simpson, C. C., & Mazzeo, S. E. (2017). Calorie counting and fitness tracking technology: Associations with eating disorder symptomatology. Eating Behaviors, 26, 89–92.

Levinson, C. A., Fewell, L., & Brosof, L. C. (2017). My Fitness Pal calorie tracker usage in the eating disorders. Eating Behaviors, 27, 14–16.

SantaBarbara, N. J., et al. (2024). Disordered eating behaviors and energy availability in resistance-trained athletes. Journal of the International Society of Sports Nutrition, 21(1).

Mountjoy, M., Sundgot-Borgen, J., Burke, L., Ackerman, K. E., Blauwet, C., Constantini, N., Lebrun, C., Lundy, B., Melin, A., Meyer, N., Sherman, R., Tenforde, A. S., Klungland Torstveit, M., & Budgett, R. (2018). IOC consensus statement on relative energy deficiency in sport (RED-S): 2018 update. British Journal of Sports Medicine, 52(11), 687–697.

Bleich, S. N., Wolfson, J. A., & Jarlenski, M. P. (2015). Calorie changes in chain restaurant menu items: Implications for obesity and evaluations of menu labeling. American Journal of Preventive Medicine, 48(1), 70–75.

U.S. Food and Drug Administration. (1993). Food labeling: Reference daily intakes and daily reference values; mandatory status of nutrition labeling and nutrient content revision. Federal Register, 58(3).

Veblen, T. (1899). The theory of the leisure class. Macmillan.

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