Fat is the most calorie-dense food group: each gram has nine calories, compared to four calories for carbohydrate and protein. So if the aim is to create a calorie deficit in your diet, then cutting down on high-fat foods is a good place to start.
Healthy eating guidelines recommend that a maximum of 30 percent of calories in the diet should come from fat; a low-fat diet for weight loss will typically reduce this to around 20 per cent. However, as usual, the total energy intake is what counts in determining weight loss; it would be possible to gain weight on a low-fat diet just by replacing fatty foods with high-sugar, high-calorie foods, so it is important to keep an eye on the overall balance of the diet, too.
some fats are essential for good health while an excess of others can be harmful. The fats in a low-fat diet should primarily be 'good' monounsaturated or polyunsaturated fats, such as those that are found in olive oil or oily fish, for example. Saturated fats, which are found in foods such as fatty meat and poultry skin or full-fat dairy products, should be kept to a minimum, as should 'trans fats' – hydrogenated vegetable oils, which are most often found in processed foods.
Low Carb diets will control the amount of fat in different ways – for example, by recommending eating only foods that have 4 grams of fat or less per 100 g, or by having a system for counting or measuring fatty foods.