Effect of a plant-based, low-fat diet versus an animal-based, ketogenic diet on ad libitum energy intake

Nat Med. 2021 Feb;27(2):344-353. doi: 10.1038/s41591-020-01209-1. Epub 2021 Jan 21.

Abstract

The carbohydrate-insulin model of obesity posits that high-carbohydrate diets lead to excess insulin secretion, thereby promoting fat accumulation and increasing energy intake. Thus, low-carbohydrate diets are predicted to reduce ad libitum energy intake as compared to low-fat, high-carbohydrate diets. To test this hypothesis, 20 adults aged 29.9 ± 1.4 (mean ± s.e.m.) years with body mass index of 27.8 ± 1.3 kg m-2 were admitted as inpatients to the National Institutes of Health Clinical Center and randomized to consume ad libitum either a minimally processed, plant-based, low-fat diet (10.3% fat, 75.2% carbohydrate) with high glycemic load (85 g 1,000 kcal-1) or a minimally processed, animal-based, ketogenic, low-carbohydrate diet (75.8% fat, 10.0% carbohydrate) with low glycemic load (6 g 1,000 kcal-1) for 2 weeks followed immediately by the alternate diet for 2 weeks. One participant withdrew due to hypoglycemia during the low-carbohydrate diet. The primary outcomes compared mean daily ad libitum energy intake between each 2-week diet period as well as between the final week of each diet. We found that the low-fat diet led to 689 ± 73 kcal d-1 less energy intake than the low-carbohydrate diet over 2 weeks (P < 0.0001) and 544 ± 68 kcal d-1 less over the final week (P < 0.0001). Therefore, the predictions of the carbohydrate-insulin model were inconsistent with our observations. This study was registered on ClinicalTrials.gov as NCT03878108 .

Publication types

  • Randomized Controlled Trial
  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Body Composition
  • Body Mass Index
  • Diet, Fat-Restricted / adverse effects
  • Diet, Ketogenic / adverse effects
  • Diet, Vegetarian / adverse effects
  • Dietary Carbohydrates / metabolism
  • Dietary Fats / metabolism
  • Energy Intake
  • Energy Metabolism / physiology*
  • Female
  • Humans
  • Insulin / genetics
  • Insulin / metabolism*
  • Male
  • Middle Aged
  • Obesity / diet therapy
  • Obesity / epidemiology
  • Obesity / metabolism*
  • Obesity / pathology
  • Overweight / diet therapy
  • Overweight / epidemiology
  • Overweight / metabolism*
  • Weight Loss

Substances

  • Dietary Carbohydrates
  • Dietary Fats
  • Insulin

Associated data

  • ClinicalTrials.gov/NCT03878108