Low-fat diet sheet

Is fat bad for me?

For several decades, the standard advice to people who want to lose weight has been to eat a low-fat diet. A diet which is low in fat and high in fruit, vegetables whole grain fibre is likely to be healthy. This is why it is the basis of many weight loss programmes such as Weightwatchers and Slimming World.

However, evidence suggests that a diet high in carbohydrates - particularly sugar - is a common trigger for obesity in many people and that eating fat is not what makes us gain weight. In this case, a low carbohydrate diet may be an effective way to lose weight - if approached in a healthy way.

So which should you choose? Research shows both low-fat and low-carbohydrate diets can be effective¹. You should find an eating pattern that works well for you, taking into account your lifestyle and what sort of foods you like.

Fat content by food type

The following table is a rough guide to which foods are higher or lower in fat. Different brands may vary in their fat content - get into the habit of looking at labels when you shop and learn which brands are lower in fat. Fat consumption will also depend on portion size.

Low-fat diets and your weight

Energy in food is measured in calories - also known as kcal. It was thought that if you want to lose weight, you need to eat fewer calories per day than you burn off. However, the science around losing weight is changing and we know there are a lot of factors involved in weight gain and weight loss.

Foods which are high in fat contain a lot of calories, so cutting down on fatty foods is one way of helping losing weight. Very sugary foods also contain quite a lot of calories, but fat contains around twice as many calories as sugar per 100g. If you have gallstones, cutting out fats is incredibly important, which is where a low fat diet will be useful.

See Healthy Eating and Weight Reduction - How to Lose Weight for more information.

Patient picks for Healthy eating

What is the Atlantic diet?

More about fats

Not all fat is bad. Although all fats are high in calories, we need some fat in our diet as some types are good for our health. For example, vitamins A,D,E and K dissolve in fat, which helps our bodies absorb them. A low-fat diet might affect our intake of these vitamins.

The different types of fat include the following:

1. Saturated fats - bad for your heart

Saturated fats are mainly found in animal products such as meat, in lard, and in dairy products such as butter and full-cream milk. Meat and dairy products have a useful role in a healthy diet - however, it's better to avoid the fattier cuts of meat and use semi-skimmed or skimmed milk. Eating less saturated fat may reduce your risk of having a heart attack.

Some cheeses are high in fat - particularly cream cheese and hard cheeses such as cheddar and parmesan. But you may find that a smaller portion of a more strong-tasting cheese is more satisfying than a larger amount of softer cheese which may be lower in fat.

2. Trans fats - generally bad

Trans fats are oils which have come from vegetables but have been processed to make them hard, so that they are easier to use in food. They are often used in processed foods, and in commercially made cakes, biscuits and pastries. Food labels may call them partially hydrogenated oils. Trans fats are generally bad for you and there is no place for them in a healthy diet.

3. Unsaturated fats - good for you

These mainly come from vegetables, nuts and fruits. They are divided into:

• Polyunsaturated fats, such as sunflower oil and corn oil.

• Mono-unsaturated fats, such as olive oil and rapeseed oil.

• Omega-3 fatty acids. These come mainly from oily fish such as pilchards, sardines, salmon, mackerel and fresh (not tinned) tuna. Omega-3 fatty acids are also present in some nuts and seeds, especially linseeds.

Omega-3 fatty acids may help prevent heart disease and improve your health in other ways.

See our Cholesterol page for more details about reducing your cholesterol level.

Unsaturated fats contain as many calories as saturated fats, but can form part of a healthy diet. If you are trying to lose weight, just make sure that you are not eating too much unsaturated fat.

Food labels

Foods contain a mixture of saturated and unsaturated fats. Food labels often list the amounts of each type of fat in the food - or at least how much of the fat in the food is saturated.

As a rule, we should aim to limit our intake of saturated fats and, when we use fats and oils, mainly choose those high in unsaturated fats.

Food labels also show how many calories are in the food. So, it is good to get into the habit of reading food labels when you shop.

Further reading

1. 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.