Limited evidenceMyth check

Eating fat makes you fat

Dietary fat is not stored as body fat in some special way: at equal calories, low-fat and higher-fat diets lead to similar weight loss in long trials. Fat is energy-dense (about 9 kcal per gram), so it is easy to overshoot calories with it, but the same is true of any food eaten in excess. Choose the fat level you can sustain.

Do this instead: stronger evidence for the same goal

The evidence for this is limited. These have better research behind them:

Low-carb vs low-fat diets Strong evidence
When calories and protein are similar, low-carbohydrate and low-fat diets produce about the same fat loss over a year or more.
Calorie deficit Strong evidence
Fat loss requires eating fewer calories than you burn for weeks to months; every diet that works does this, whatever it is called.
High-protein diet while dieting Strong evidence
Eating more protein during a calorie deficit helps keep lean mass and gives a small extra fat loss compared with a standard-protein diet of the same calories.
Self-monitoring (food logging and weighing) Moderate evidence
Tracking what you eat and weighing yourself regularly are consistently linked to more weight loss and less regain.

What the science says

Low-fat diets beat higher-fat diets for weight loss Limited evidence
Tobias and colleagues' 2015 meta-analysis of 53 trials (68,128 participants, at least 1 year) found that low-fat diets did not lead to more weight loss than other higher-fat diets, and low-carbohydrate diets produced slightly more loss (about 1.15 kg).
Healthy low-fat and low-carb diets give similar results Strong evidence
In the DIETFITS trial (Gardner and colleagues, 2018), 609 adults followed a healthy low-fat or a healthy low-carbohydrate diet for 12 months: weight change was -5.3 kg versus -6.0 kg, not significantly different.
At equal calories, macronutrient mix has small effects on fat loss Moderate evidence
Hall and colleagues (2015) kept 19 adults with obesity on a metabolic ward and cut either fat or carbohydrate by the same calories for 6 days. Fat restriction produced slightly more body fat loss (89 vs 53 g/day), the opposite of the myth, though the authors predicted the difference would shrink over longer periods.

What to do instead

Set your calorie target, keep protein high, and pick a fat and carbohydrate split you can follow; measure fat-rich foods since small portions add many calories.

Fat intakeAbout 20–35% of calories, by preference

ProteinAbout 1.6 g/kg body weight per day

Oils, nuts, nut buttersMeasure portions; 1 tablespoon of oil is about 120 kcal

Diet styleLow-fat or low-carb, whichever you can sustain

Who should be careful

People with high blood lipids, diabetes, gallbladder or pancreatic disease should set fat intake with their physician or dietitian. People with diabetes, heart, kidney or thyroid conditions, anyone with a history of an eating disorder, and anyone pregnant or considering weight-loss medication should plan weight loss with a physician or registered dietitian rather than on their own.

Supplements that help with this goal

Whey Protein Strong evidence
Higher protein helps keep muscle while you are in a calorie deficit.
Read the analysis · View on iHerb
Caffeine Strong evidence
A small boost to training output; it does not burn meaningful fat by itself.
Read the analysis · View on iHerb

Popular, but the evidence says skip

Garcinia Cambogia Limited evidence
Weight loss in trials is tiny or absent.
Read the analysis
Raspberry Ketones Limited evidence
No good human evidence for fat loss.
Read the analysis
Fat Burner Formulas Limited evidence
Mixed blends with little evidence and real safety concerns.
Read the analysis

Grades come from our supplement analyses. Purchase links are disclosed affiliate links at the store's normal price; they never affect a grade.

Frequently asked questions

Is a low-fat diet better for losing weight?

No. A meta-analysis of 53 trials found low-fat diets did no better than other higher-fat diets over at least a year.

Low-fat or low-carb?

In the 12-month DIETFITS trial, results were similar (-5.3 kg vs -6.0 kg); choose the one you can sustain.

Why do people think fat makes you fat?

Fat is energy-dense, about 9 kcal per gram, so it is easy to overeat calories, but at equal calories it does not cause more fat gain.

Scientific references

Effect of low-fat diet interventions versus other diet interventions on long-term weight change in adults: a systematic review and meta-analysis
Tobias DK et al. · Lancet Diabetes Endocrinol, 2015 · PMID 26527511
Effect of Low-Fat vs Low-Carbohydrate Diet on 12-Month Weight Loss in Overweight Adults and the Association With Genotype Pattern or Insulin Secretion: The DIETFITS Randomized Clinical Trial
Gardner CD et al. · JAMA, 2018 · PMID 29466592
Calorie for Calorie, Dietary Fat Restriction Results in More Body Fat Loss than Carbohydrate Restriction in People with Obesity
Hall KD et al. · Cell Metab, 2015 · PMID 26278052

More myth checks

The anabolic window (eat protein within 30 minutes of training) Limited evidence
The idea that you must get protein in within 30-60 minutes after lifting or lose your gains does not hold up.
Muscle confusion (constantly change exercises to keep growing) Limited evidence
Muscles do not need to be "confused" to grow; they need a progressively harder stimulus.
Spot reduction (crunches burn belly fat, leg work burns thigh fat) Limited evidence
Training a body part does not preferentially burn the fat on top of it.
Cardio before weights ruins your gains (exercise order matters) Moderate evidence
This one is partly true.
High reps with light weights tone, heavy weights bulk Limited evidence
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No pain, no gain (soreness means the workout worked) Limited evidence
Muscle soreness mostly reflects how unaccustomed a workout was, not how much muscle it will build.