Dietary Fat Explained: How Much You Need and Which Kinds

For decades, dietary fat was treated as the enemy. Then the pendulum swung, and some diets made it the hero. The truth sits in between: fat is essential for health, but it is also the most calorie-dense nutrient, so the amount and type matter.

Why You Need Fat

• It supplies essential fatty acids your body cannot make.
• It helps absorb vitamins A, D, E and K.
• It supports hormone production, including sex hormones.
• It makes food satisfying and tasty.

How Much?

Many guidelines suggest that around 20 to 35 percent of daily calories come from fat. Going very low — below about 15 to 20 percent for long periods — can affect hormones and makes meals less satisfying. Going very high leaves less room for protein and carbohydrates.

At 9 calories per gram, compared with 4 for protein and carbohydrates, fat adds up quickly. A tablespoon of olive oil has about 120 calories.

The Types of Fat

• Unsaturated fats: found in olive oil, nuts, seeds, avocados and fish. Associated with better heart health and generally recommended as the main fats in your diet.
• Omega-3 fats: a type of unsaturated fat found mainly in oily fish like salmon, sardines and mackerel, plus smaller amounts in walnuts, chia and flaxseeds.
• Saturated fats: found in butter, fatty meats, cheese and coconut oil. Fine in moderate amounts, but health guidelines typically recommend limiting them.
• Trans fats: industrially produced trans fats are linked to heart disease and are best avoided. Many countries now restrict them.

Practical Choices

• Cook with olive oil or rapeseed oil more often than butter.
• Eat oily fish once or twice a week, or consider an omega-3 supplement if you do not.
• Use nuts and seeds as snacks or toppings — but measure them, since handfuls grow quickly.
• Choose leaner cuts of meat and moderate portions of cheese.

Fat and Fat Loss

Eating fat does not directly make you fat, and low-fat diets are not better for fat loss than other approaches when calories are equal. But because fat is so calorie-dense, hidden fats in cooking oils, dressings and sauces are often where unnoticed calories come from.