Up Two Kilos After a Big Weekend? Why Most of It Isn't Fat

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Episode Summary
In this solo Monday episode, Mikki tackles a question she gets constantly from clients and on social media: why the scales can jump two kilos after a big weekend when that much fat gain seems impossible. She traces the familiar rule that a kilo of fat is worth about 7,700 calories (3,500 per pound) back to Wishnofsky's 1958 paper. She explains why it is a reasonable estimate of the energy stored in mostly-fat body weight, but a poor prediction of how much fat a given surplus will add.
Using overfeeding studies, including the Levine NEAT study and the Bouchard identical twin study, Mikki works through three problems with the rule: extra food isn't all stored, not all weight gain is fat, and energy balance shifts as your body changes. She then reruns the maths on a genuinely big weekend and shows why a Monday-morning jump is mostly glycogen, water, salt and food in transit. That understanding should change what you do next.
Key Topics
  • Where the 7,700 calorie (3,500 kcal per pound) rule came from, and why it is defensible as an estimate of the energy in a kilo of mostly-fat body weight
  • The difference between a kilo of pure lipid, a kilo of adipose tissue and a kilo on the scales, which can represent anything from about 1,000 to more than 9,000 calories
  • Why digesting and storing food costs energy, and why a carbohydrate surplus is stored a little less efficiently than a fat surplus without meaning carbs cause more fat gain
  • What extra protein changes during overfeeding: in a metabolic ward study fat gain was similar across protein intakes, but higher-protein diets added lean tissue and raised resting energy expenditure
  • How NEAT (non-exercise activity thermogenesis) explained much of the tenfold difference in fat storage between people eating the same surplus
  • The identical twin overfeeding study: about 11 kg predicted by the rule, 8.1 kg gained on average, with a range of 4.3 to 13.3 kg and responses that clustered within twin pairs. Mikki notes that these were young men, and the results can't be mapped directly onto women in perimenopause
  • How glycogen and water, sodium, alcohol and food in the gut drive short-term jumps on the scales, and why the water-to-glycogen ratio isn't as fixed as often stated
  • Why energy balance isn't static, and why the energy content of each kilo lost is lower early in a diet and in leaner people
  • Rerunning the maths: roughly 9,000–11,000 surplus calories to add a kilo of fat tissue, and around 400–500 g of fat at most from a 4,500 calorie weekend surplus
  • Why the 7,700 rule creates false precision in both directions, from panic after a big weekend to disappointment after week one of a new plan
Chapters
00:00 Introduction: the Monday morning weigh-in
02:52 Where the 7,700 calorie rule comes from
05:17 Why extra food isn't all stored
07:30 NEAT and the twin overfeeding study
10:29 Glycogen, water and short-term weight gain
13:00 Why energy balance isn't static
16:15 What a kilo on the scales really means
18:09 Big weekends, new diets and what to do next
Guest / Resources
  • Wishnofsky (1958), Caloric Equivalents of Gained or Lost Weight, American Journal of Clinical Nutrition
  • Horton et al. (1995), Fat and carbohydrate overfeeding in humans: different effects on energy storage, American Journal of Clinical Nutrition
  • Antonio et al. (2014), The effects of consuming a high protein diet (4.4 g/kg/d) on body composition in resistance-trained individuals, Journal of the International Society of Sports Nutrition
  • Bray et al. (2012), Effect of dietary protein content on weight gain, energy expenditure, and body composition during overeating, JAMA
  • Levine, Eberhardt and Jensen (1999), Role of nonexercise activity thermogenesis in resistance to fat gain in humans, Science
  • Bouchard et al. (1990), The response to long-term overfeeding in identical twins, New England Journal of Medicine
  • Olsson and Saltin (1970), Variation in total body water with muscle glycogen changes in man, Acta Physiologica Scandinavica
  • Hall and Chow (2013), Why is the 3500 kcal per pound weight loss rule wrong?, International Journal of Obesity
  • Leibel, Rosenbaum and Hirsch (1995), Changes in energy expenditure resulting from altered body weight, New England Journal of Medicine
  • Heymsfield et al. (2012), Energy content of weight loss: kinetic features during voluntary caloric restriction, Metabolism

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