The Study
Resting Metabolic Rate, Body Composition and Thyroid Hormones
This study watched what happened to 27 women when they ate very little food for two weeks. It saw that their bodies burned fewer calories and their thyroid hormone went down. But it didn't compare them to people who ate normally, so we can't say the diet caused those changes — maybe they would've happened anyway.
Analysis score
Maximum 44 for a cross-sectional study.
Where the score came from
When obese women ate almost nothing for 15 days, their bodies slowed down to save energy, burning fewer calories even after losing weight.
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 531 / 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.
- 1Yes — this drop in calorie burn is bigger than expected from weight loss alone, meaning the body actively slows metabolism to conserve energy during extreme dieting.
- 2They lost 6 kg, their calorie burn dropped from 1793 to 1569 kcal/day, and a key thyroid hormone (T3) fell from 1.1 to 1.0 μg/L.
Score breakdown, methodology, conflicts of interest, evidence analysis & raw study data
Publication
Journal
Horm. metab. Res.
Year
1990
Authors
E. Cavallo, F. Armellini, M. Zamboni, R. Vicentini, M. Milani, O. Bosello
Related Content
Claims (6)
When thyroid hormone levels are low, the body's metabolic rate decreases, leading to less fat burning, weight gain, constipation, and fatigue.
After 15 days of a very low-calorie diet, obese women experience a drop in resting metabolic rate that is larger than what would be predicted by the amount of weight lost, showing a measurable physiological adjustment to reduced energy intake.
In obese women, consuming a very low-calorie diet for 15 days results in a measurable drop in resting metabolic rate and a reduction in serum triiodothyronine levels.
In obese women, a 15-day very low-calorie diet leads to lower levels of serum triiodothyronine (T3) and a lower resting metabolic rate.
Obese women who follow a very low-calorie diet for 15 days lose an average of 6 kilograms, mostly from muscle and other non-fat tissues, and their resting metabolic rate decreases as a result.
After 15 days of a very low-calorie diet, the body burns fewer calories at rest than expected based on the amount of weight lost, indicating an additional reduction in metabolic rate beyond what body composition changes alone would explain.
Not medical advice. For informational purposes only. Always consult a qualified healthcare professional before making health decisions.