Low-Fat Diets: A Review ★★★☆☆

By R.Davies, PhD・Diet Atlas
Published May 17, 2026 | 3 min read

The low-fat diet limits fat intake to at least under 30% of daily calories, which is less than the typical Western diet's fat intake of around 40%. The low-fat diet became popular in the 1980s after some studies linked dietary fat, particularly saturated fat, to cardiovascular disease. Very low-fat diets limit fat to less than 15% of total calories and are sometimes used to treat specific medical conditions.

Dietary fat has a higher calorie density (9 calories per gram) and provides more than twice the calories of carbohydrates or protein (4 calories per gram) gram for gram. So, reducing fat intake, in theory, allows for larger volumes of food for the same calories, which may help reduce calorie intake and body weight. Additionally, reducing saturated fat was believed to decrease cardiovascular disease risk, though this relationship has proven to be more complicated than initially thought.

Low-fat diets generally emphasise eating lean proteins such as skinless poultry, fish, egg whites, and low-fat dairy products, along with fruits, vegetables, whole grains, and legumes. While limiting fatty meats, full-fat dairy, butter, oils, nuts, seeds, fried foods, and processed items high in fat. 

As fat intake is reduced, carbohydrates usually make up a larger proportion of the diet, making the ‘quality’ of carbohydrate intake especially important. For decades, public health guidelines have promoted low-fat diets, but modern science now focuses more on reducing specific types of fats first rather than on reducing the total amount of fat.

Pros

Low-fat diets show clear cardiovascular health benefits, particularly when saturated fats are replaced with healthier unsaturated fats or ‘complex’ (whole food, whole grain) carbohydrates. There is evidence showing that cardiovascular health risks can be reduced further when weight loss occurs, which is also reported in overweight or obese people who follow the diet.

When well-planned with adequate protein and healthy carbohydrates from whole grains, fruits, and vegetables, low-fat diets can provide complete nutrition (and all-round health). The emphasis on plant-based foods also naturally increases intake of dietary fibre, vitamins, minerals, and phytonutrients. The diet's accessibility and compatibility with many ‘cultural’ (carbohydrate-based) eating patterns contribute to its appeal.

Cons

Evidence for low-fat diets' superiority over other diets is mixed. Long-term studies show no consistent advantage over other balanced diets for weight loss, with many studies demonstrating equal outcomes after 12 months. Researchers generally report little differences in health markers for low-fat dieters (e.g., lipid profile, blood pressure, or blood sugar levels) compared to diets with moderate fat intake.

Very-low-fat diets (below 15% of calories) can increase the risk of nutrient deficiencies and higher intake of refined carbohydrates or sugars. Severely restricting dietary fat also likely reduces the intake of essential fats and fat-soluble vitamins (A, D, E, K) that are needed for good health. Studies also report decreased testosterone levels in men following very-low-fat diets, raising concerns about hormonal effects.

The diet's lower ‘satiety’ compared to higher-fat or higher-protein diets may be challenging for some people who struggle to control their appetite. Fat adds flavour to food and helps it feel satisfying, so restricting it can make meals less enjoyable. In practice, many people find low-fat diets difficult to sustain in the long term.

Bottom Line

Low-fat diets can support modest weight loss, cardiovascular and metabolic health benefits when thoughtfully done. However, low-fat diets are not clearly superior to other balanced diets and can potentially pose risks if taken to extremes. Modern evidence supports promoting fat quality over quantity, making moderate-fat diets (i.e., 15-30% total calorie intake) with healthy fat sources preferable for most people.

Sources

Astrup A et al. The role of low-fat diets in body weight control: a meta-analysis of ad libitum dietary intervention studies. Int J Obes Relat Metab Disord. 2000 Dec;24(12):1545-52. PMID: 11126204

Daley SF, Goldin J. Low-Fat Diet. [Updated 2026 Jan 31]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2026 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK553097/

Gardner CD et al. 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. JAMA. 2018 Feb 20;319(7):667-679. PMID: 29466592

Park S et al. Very-low-fat diets may be associated with increased risk of metabolic syndrome in the adult population. Clin Nutr. 2016 Oct;35(5):1159-67. PMID: 26602244

Shai I et al. Dietary Intervention Randomized Controlled Trial (DIRECT) Group. Weight loss with a low-carbohydrate, Mediterranean, or low-fat diet. N Engl J Med. 2008 Jul 17;359(3):229-41. PMID: 18635428

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. Lancet Diabetes Endocrinol. 2015 Dec;3(12):968-79. PMID: 26527511

Further Reading

High Protein Diet: A Review

Blue Zone Diet: A Review

Ketogenic Diet: A Review

Published: May 17, 2026

Lead Author: R.Davies, PhD | Author Bio

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