Systematic reviewindependent cross-checkabstract checked★ key study I-LIFE-101 in-depth review

Eating less fat and body weight

Effects of total fat intake on body fatness in adults.

Overview

Hooper L et al.. Cochrane Database Syst Rev 2020 · PMID 32476140 · DOI 10.1002/14651858.CD013636

People who ate less fat weighed about 1.4 kg less on average than those who ate more fat, even without trying to lose weight.

Does the study support the specific claim? Partly · Methodological quality: high

Study explained simply

What did the researchers want to find out?: Assess fat intake and body fatness.
How was the study done?: Cochrane review of 37 RCTs.
How many people, animals or samples were studied?: 57,079 adults.
What was actually found?: Small weight reduction with less fat.
How large was the observed effect?: MD -1.4 kg (-1.7 to -1.1).
What do the results mean in everyday life?: Fat is not the main driver of weight gain, but it is not irrelevant either.
What are the study's limitations?: Small effect.
What does it say about Elawady's specific claim?: Partly limits the claim.
Do the results apply to Germany and Europe?: Applies; same physiology.
What can explicitly not be concluded from this study?: Effects of very high fat intakes such as unlimited ghee.

Authors: Hooper L et al.
Journal: Cochrane Database Syst Rev
Year: 2020
Identifier: PMID 32476140 DOI 10.1002/14651858.CD013636
Verification: verified – PubMed efetch 2026-10-26; Crossref update-to/updated-by check
Retracted: no
Corrections: none
Extent checked: abstract only
Conflicts of interest and funding: WHO funded part of the update (stated).

Does the proportion of energy from fat affect body fatness in people not aiming to lose weight?

Study design: Systematic review – Cochrane systematic review and meta-analysis of RCTs >=6 months
Population: Adults not trying to lose weight
Country: International
Period: Search to Oct 2019
Sample size: 37 RCTs, 57,079 participants
Inclusion and exclusion criteria: not stated in abstract

Results: Lower fat: body weight MD -1.4 kg (95% CI -1.7 to -1.1; 26 RCTs, 53,875 participants; I2 75%), BMI -0.5 kg/m2 (-0.6 to -0.3), waist -0.5 cm (-0.7 to -0.2), body fat -0.3% (-0.6 to 0.00). Greater weight loss with greater fat reduction, lower baseline fat and higher baseline BMI.
Absolute risks: not reported
Authors' conclusion: Consistent, stable but small effect of lower fat intake on body fatness.

Effect small (1.4 kg); stats/I-LIFE-101_fat_body_weight.py.

Fat intake contributes a small amount to body weight - so fat is not irrelevant, but it is not 'the origin' of weight gain either.

Universal biology; applies in Europe and Egypt.

Limits the claim: fat share has a small, real effect.

Multidimensional assessment
Multidimensional assessment
Authenticity of the source	verified
Methodological quality	high
Risk of bias	low
Precision of results	high
Directness	direct
Reproducibility	replicated
Consistency with the overall evidence	consistent
Regional transferability	high
Adequacy of the interpretation (by the archive)	not applicable