Fats
Dietary fat is a concentrated source of energy that your body needs for hormones, cell membranes and absorbing vitamins A, D, E and K. The type of fat matters as much as the amount.
On this page
Why you need fat
- Essential fatty acids. Your body can't make omega-3 (ALA) or omega-6 (LA) fats, so they have to come from food.
- Vitamins A, D, E and K dissolve in fat, so you need some fat to absorb them.
- Hormones. Very low-fat diets can modestly lower testosterone in men1.
- Flavour and fullness. Fat slows digestion and makes food satisfying.
Fat has 9 kcal per gram, more than twice as much as protein or carbs. That's why oils, butter and nuts add up quickly when you're counting calories.
The types of fat
| Type | Where you find it | Effect | Verdict |
|---|---|---|---|
| Monounsaturated | Olive and rapeseed oil, avocados, almonds, peanuts | Helps keep LDL ("bad") cholesterol in check | ✅ Base your fats on these |
| Polyunsaturated: omega-3 | Oily fish (salmon, mackerel, sardines), walnuts, flax, chia | Heart health; EPA and DHA from fish are the best studied | ✅ Oily fish once a week |
| Polyunsaturated: omega-6 | Sunflower and corn oil, many seeds | Lowers LDL cholesterol when it replaces saturated fat | ✅ Fine as part of a mix |
| Saturated | Butter, cheese, fatty and processed meat, coconut and palm oil, cakes and pastries | Raises LDL cholesterol | ⚠️ Keep within limits |
| Trans | Some fried and baked foods (partially hydrogenated oils); small amounts in meat and dairy | Raises LDL and lowers HDL ("good") cholesterol | ❌ Keep as low as you can |
Research spotlight
In a Cochrane review of 15 randomised trials, cutting down on saturated fat reduced combined cardiovascular events, such as heart attacks and strokes, by about 17%. Replacing it with polyunsaturated fats or starchy foods looked the most useful swaps.
How much fat you need
| Guideline | Amount |
|---|---|
| Saturated fat, men (UK)3 | No more than 30 g a day |
| Saturated fat, women (UK)3 | No more than 20 g a day |
| Saturated fat (as a share of calories)4 | No more than 10% of calories |
| Total fat for athletes and lifters5 | About 20–35% of calories |
| Oily fish6 | At least one 140 g portion a week |
When cutting, it's tempting to slash fat to save calories. Try not to go below about 20% of your calories for long: you need it for hormones and vitamin absorption, and meals get much less satisfying.
Where the fat in your diet comes from
| Food | Per 100 g | Per serving |
|---|---|---|
| Olive oil (mostly monounsaturated) | 100 g | 11 g1 tbsp (11 g) |
| Butter (mostly saturated) | 82 g | 8.2 g10 g |
| Walnuts (rich in omega-3) | 65 g | 19.5 g30 g handful |
| Almonds (mostly monounsaturated) | 50 g | 15 g30 g handful |
| Peanut butter (mono and poly) | 50 g | 16 g2 tbsp (32 g) |
| Dark chocolate 70–85% (mostly saturated) | 43 g | 8.6 g20 g |
| Cheddar (mostly saturated) | 34 g | 10.2 g30 g |
| Avocado (mostly monounsaturated) | 15 g | 10.5 gHalf (70 g) |
| Salmon, farmed, cooked (omega-3) | 12 g | 14.4 g1 fillet (120 g) |
Common myths
MythEating fat makes you fat.
FactFat is calorie-dense, but weight gain comes from eating more calories than you use, from any source.
MythCoconut oil is a superfood.
FactIt's about 80–90% saturated fat and raises LDL cholesterol compared with oils like olive or rapeseed9.
MythLow-fat products are always the healthier choice.
FactSome replace fat with sugar or starch. Check the label for calories and sugar, not just fat.
Track this in NutriLog
Keep an eye on fat and saturates
NutriLog tracks fat and saturates for every meal and flags high-saturate foods using the UK traffic-light system.
Free to start. Full macro tracking is part of NutriLog Pro.
References
- Whittaker J, Wu K. Low-fat diets and testosterone in men: systematic review and meta-analysis of intervention studies. J Steroid Biochem Mol Biol. 2021;210:105878. doi:10.1016/j.jsbmb.2021.105878
- Hooper L, Martin N, Jimoh OF, Kirk C, Foster E, Abdelhamid AS. Reduction in saturated fat intake for cardiovascular disease. Cochrane Database Syst Rev. 2020;5:CD011737. doi:10.1002/14651858.CD011737.pub2
- NHS. Fat: the facts. nhs.uk.
- Scientific Advisory Committee on Nutrition. Saturated fats and health. Public Health England, 2019.
- Thomas DT, Erdman KA, Burke LM. American College of Sports Medicine Joint Position Statement: Nutrition and Athletic Performance. Med Sci Sports Exerc. 2016;48(3):543-568. doi:10.1249/MSS.0000000000000852
- NHS. Fish and shellfish. nhs.uk.
- Public Health England. McCance and Widdowson's The Composition of Foods Integrated Dataset (CoFID). GOV.UK, 2021.
- U.S. Department of Agriculture, Agricultural Research Service. FoodData Central. fdc.nal.usda.gov.
- Neelakantan N, Seah JYH, van Dam RM. The effect of coconut oil consumption on cardiovascular risk factors: a systematic review and meta-analysis of clinical trials. Circulation. 2020;141(10):803-814. doi:10.1161/CIRCULATIONAHA.119.043052