Low fat: the diet that ruled the 90s and lost the argument (mostly).
Fat-free yoghurt, fat-free biscuits, fat-free everything. We did it for thirty years and got fatter. The low-fat diet wasn't a lie, but it was oversold. Here's what the big trials really found.
The short version
- What it is
- Fat cut to about 20–30% of your calories. More bread, rice, fruit and vegetables instead.
- Good for
- A small, steady weight drop if you used to eat a lot of fat. Less saturated fat, better cholesterol.
- Bad at
- Beating other diets. And the "low-fat" products are often sugar in disguise.
- Evidence
- Moderate. Lots of big trials, mostly unexciting results.
- Our take
- Wrong target. Cut the bad fats and the junk carbs, keep the good fats. We don't plan low-fat.
What the low-fat diet actually is
Exactly what it says. You eat less fat: less butter, less oil, less cheese, less fatty meat, fewer fried foods. To fill the gap, you eat more carbohydrates: bread, pasta, rice, potatoes, fruit. Strict versions push fat down to 10–20% of calories. Typical versions aim for 20–30%.
The idea dominated nutrition advice from the 1980s onwards. The logic seemed solid. Fat has 9 calories per gram, carbs and protein only 4.8 Saturated fat raises cholesterol. So: cut fat, lose weight, save your heart. Food companies loved it and filled the shelves with fat-free products. Most of them replaced the fat with sugar and starch, and nobody got thinner.
How it works in your body
Fat is the most calorie-dense thing you can eat. Gram for gram, it has more than twice the calories of sugar.8 So if you cut fat and don't replace all those calories, you eat less overall and lose a little weight. That's the whole mechanism. There's no special fat-burning switch.
The heart part works through cholesterol. Saturated fat, found in butter, fatty meat, cheese, coconut and palm oil, pushes up LDL ("bad") cholesterol. Eat less of it and LDL tends to drop. The catch: what you eat instead matters as much as what you cut. Swap butter for olive oil and your heart wins. Swap it for white bread and sugar and you've gained very little.
What you eat, what you don't
Eat
- Vegetables and fruit, lots of both
- Beans, lentils, chickpeas
- Whole grains: oats, brown rice, wholegrain bread
- White fish, skinless chicken, egg whites
- Low-fat yoghurt and milk (unsweetened)
- Potatoes, boiled or baked, not fried
Forget it
- Butter, lard, cream, fatty cheese
- Fried food, pastries, crisps
- Fatty and processed meat: sausages, salami, bacon
- Lots of oil, nuts, avocado (strict versions)
- Coconut and palm oil
Alcohol on a low-fat diet
OK, now and then
- A glass of dry wine
- A small beer or light beer
- Spirits with soda water and lime
Wrecks the point
- Cream liqueurs and creamy cocktails
- Sweet cocktails, alcopops, cider
- Anything with juice, cola or tonic
- The bar snacks that come with it: crisps, nuts in salt, fries
50 Club: one dry wine or one small beer, with food.
Alcohol has no fat, which is why low-fat diets often ignore it. It still has 7 calories per gram, nearly as much as fat.8 And the WHO says no safe level of drinking has been shown.9 All the details are in our alcohol guide.
What it's good for, with proof
A small weight drop, without even trying
A Cochrane review pooled 37 trials with over 57,000 people who weren't trying to lose weight. Those who ate less fat ended up about 1.4 kg lighter than those who didn't.1 Small, but consistent: almost every trial pointed the same way. If your diet is heavy on fried food and cheese, eating less of it helps.
Less saturated fat, fewer heart problems
Here's the part of the low-fat story that holds up. Another Cochrane review looked at 15 long-term trials. Cutting saturated fat lowered the risk of heart attacks and strokes by about 17%.2 The benefit was bigger when people replaced it with unsaturated fats, like olive oil, nut and seed oils, rather than with carbs. So the lesson isn't "less fat". It's "less butter, more olive oil".
As good as low-carb, when done properly
In the DIETFITS trial, 609 adults followed either a healthy low-fat or a healthy low-carb diet for a year. Both groups were told to eat real food and skip junk. The result: 5.3 kg lost on low-fat, 6.0 kg on low-carb. No real difference.3 And in a tightly controlled US government study, people on a plant-based low-fat diet ate fewer calories than on keto.4 Low-fat can work. It just isn't the only thing that does.
The uncomfortable truth
"Eating fat makes you fat." Not more than anything else. A meta-analysis of 53 long-term trials found low-fat diets did no better than other weight-loss diets. Low-carb diets beat them by about a kilo.5 Low-fat only won against people who changed nothing at all.
"Low-fat prevents heart disease and cancer." That was the big bet. The Women's Health Initiative put almost 49,000 women on low-fat or usual diets for about eight years. Heart disease and stroke: no significant difference.6 Breast cancer: a small trend, not statistically significant.7 Decades of advice, and the largest trial ever done came back with a shrug.
Then there's the fat-free aisle. When companies take fat out, the food tastes like cardboard, so they put sugar, starch and thickeners in. Check the label on any fat-free fruit yoghurt. Low fat, high sugar is not a health food.
The risks
- The sugar swap. Cut fat, eat more white bread, sweet cereal and "light" snacks, and you've traded one problem for another.
- Losing the good fats. Strict low-fat cuts olive oil, nuts and oily fish too. These are the fats linked with fewer heart problems when they replace saturated fat.2
- Hunger. Fat slows digestion. Meals with almost none can leave you hungry an hour later, and that's when the biscuits come out.
- Blood sugar. More carbs means bigger blood sugar swings, which matters if you have type 2 diabetes or prediabetes. Talk to your doctor before a big switch.
Allergies: watch the staples
Low-fat leans on grains, dairy and lean protein. Some of those are on the EU allergen list.
| Staple | Allergen (EU list of 14)10 | Swap |
|---|---|---|
| Wholegrain bread, pasta, oats | Cereals containing gluten | Brown rice, potatoes, quinoa, certified gluten-free oats |
| Low-fat milk, yoghurt, cottage cheese | Milk | Unsweetened oat drink, soy yoghurt (if no soy allergy) |
| Egg whites | Eggs | Chicken, white fish, beans |
| Cod, haddock, plaice | Fish | Skinless chicken, lentils, tofu |
| Prawns, mussels | Crustaceans, molluscs | Chicken, white fish |
| Tofu, soy milk | Soy | Beans, lentils, chicken |
Don't do low fat if you…
- have type 2 diabetes or prediabetes and plan to replace the fat with bread, rice and sweets
- are underweight or struggle to eat enough
- are pregnant or breastfeeding and thinking of cutting oily fish
- have ever had an eating disorder: cutting a whole nutrient can turn into a rule that runs your life
If a doctor has prescribed a low-fat diet for a medical reason, follow them, not us. Healthen me asks about all of these and gives you a different plan if any apply.
How we use low fat in your plan
We don't. Low fat is an information article, not part of the engine.
Why? Because the evidence points somewhere else. The fight was never fat versus carbs. It's real food versus processed food, and good fats versus bad fats. So your plan keeps the part of low-fat that works: little butter, little fatty and processed meat, nothing deep-fried. Then it adds back what low-fat threw away: olive oil, nuts and oily fish, the backbone of the Mediterranean diet.
If you love a lighter way of eating, the DASH diet and the whole-food plant-based approach are low-fat done well. Both are explained on Healthen.
This article is general information, not medical advice. If you have a medical condition or take medication, talk to your doctor before changing how you eat.
Sources
- Hooper L et al. Effects of total fat intake on body fatness in adults. Cochrane Database of Systematic Reviews 2020;6:CD013636. doi.org/10.1002/14651858.CD013636
- Hooper L et al. Reduction in saturated fat intake for cardiovascular disease. Cochrane Database of Systematic Reviews 2020;8:CD011737. doi.org/10.1002/14651858.CD011737.pub3
- Gardner CD et al. Effect of low-fat vs low-carbohydrate diet on 12-month weight loss in overweight adults (DIETFITS). JAMA 2018;319(7):667–679. doi.org/10.1001/jama.2018.0245
- Hall KD et al. Effect of a plant-based, low-fat diet versus an animal-based, ketogenic diet on ad libitum energy intake. Nature Medicine 2021;27:344–353. doi.org/10.1038/s41591-020-01209-1
- Tobias DK et al. Effect of low-fat diet interventions versus other diet interventions on long-term weight change in adults: a systematic review and meta-analysis. The Lancet Diabetes & Endocrinology 2015;3(12):968–979. doi.org/10.1016/S2213-8587(15)00367-8
- Howard BV et al. Low-fat dietary pattern and risk of cardiovascular disease: the Women's Health Initiative Randomized Controlled Dietary Modification Trial. JAMA 2006;295(6):655–666. doi.org/10.1001/jama.295.6.655
- Prentice RL et al. Low-fat dietary pattern and risk of invasive breast cancer: the Women's Health Initiative Randomized Controlled Dietary Modification Trial. JAMA 2006;295(6):629–642. doi.org/10.1001/jama.295.6.629
- Regulation (EU) No 1169/2011 on food information to consumers, Annex XIV (energy conversion factors: fat 9 kcal/g, carbohydrate and protein 4 kcal/g, alcohol 7 kcal/g). eur-lex.europa.eu/eli/reg/2011/1169/oj
- WHO Regional Office for Europe. No level of alcohol consumption is safe for our health. News release, 4 January 2023. who.int/europe/news/item/04-01-2023-no-level-of-alcohol-consumption-is-safe-for-our-health
- Regulation (EU) No 1169/2011 on food information to consumers, Annex II (the 14 allergens). eur-lex.europa.eu/eli/reg/2011/1169/oj