The Study
Thermic effect of feeding carbohydrate, fat, protein and mixed meal in lean and obese subjects.
This study looked at how much energy people burned after eating different foods and noticed that obese people didn't burn as much energy after eating fat as lean people did. But it didn't change what people ate or who they were — it just watched and compared. So we can say there's a difference, but we can't say eating fat causes obesity.
Analysis score
Maximum 44 for a cross-sectional study.
Where the score came from
After eating, your body burns extra calories to digest food — but this doesn't work as well in some obese people when they eat fat.
Where does this study sit?
Reviews of RCTs (Meta-analyses)
Max 100Randomized Trials
Max 90Reviews of Cohort Studies
Max 85Cohort Studies
Max 72Reviews of Case-Control Studies
Max 63Case-Control Studies
Max 58Cross-Sectional & Case Series
Max 50Expert Opinion
Max 544 / 100
Quality score
Snapshots of a population at a single point in time, or descriptions of small groups. Can identify correlations and prevalence, but cannot determine cause and effect.
Key takeaways
Summary
Based on the study abstract and findings.
- 1This means obese people may store more fat after eating fatty foods because their bodies don't burn off the extra calories as well — even though they digest the food just as fast.
- 2Lean people burn 14.4% more energy after eating fat; obese people burn almost nothing (-0.9%).
- 3After mixed meals, lean people burn 25% more energy; obese people burn only 13% more.
- 4Both groups burn the same amount after eating carbs or protein.
Score breakdown, methodology, conflicts of interest, evidence analysis & raw study data
Publication
Journal
The American journal of clinical nutrition
Year
1985
Authors
R. Swaminathan, R. King, J. Holmfield, R. Siwek, M. Baker, J. Wales
Related Content
Claims (6)
Eating protein causes the body to burn more calories during digestion than eating the same amount of carbohydrates or fats.
After eating carbohydrates or protein, obese and lean adults burn the same amount of energy as heat, suggesting that obesity-related metabolic differences affect fat digestion but not how the body uses energy after eating carbs or protein.
Obese adults generate less heat from digesting dietary fat than lean adults, but their heat production from digesting glucose and protein is the same. This difference is not due to slower digestion.
Obese adults digest glucose and fatty meals at the same rate as lean individuals, and the lower heat production from fat in obese people is not caused by slower digestion or absorption.
When obese adults eat fat, their metabolism increases very little, while in lean adults, eating fat causes a clear increase in metabolism.
After eating a mixed meal, adults with obesity have a smaller increase in metabolic rate than adults with normal weight, resulting in less energy being burned after the meal.
Not medical advice. For informational purposes only. Always consult a qualified healthcare professional before making health decisions.