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What is dieting?

Reducing body fat by changing what you eat.

What does dieting do?

How long does dieting last?

The effects of dieting only last while you maintain the diet. For dieting to be successful, it needs to be a sustainable permanent lifestyle change.

How do I stay safe?

Do not attempt to radically reduce calories by eating extremely small amounts unless you have been told to do so by a doctor.

Information for under 18s

While your body is still developing, it is especially important that you eat enough food. The NHS has a guide giving advice on healthy eating for teens.

Why might I want to diet?

Dieting is a way to reduce body fat by changing what you eat. You may be interested in losing body fat:

  • To reduce chest, hip or buttock size.
  • To make muscles more defined.
  • To prepare for medical procedures. A number of UK surgeons who perform gender related surgeries require people to have a body mass index (BMI) below a certain threshold before they will operate.

Why might I not want to diet?

It is important to have a healthy and balanced diet. However, just because you have more body fat than you would like to, that doesn’t necessarily mean that your diet is unhealthy.

Here are some reasons you might not want to change your diet:

  • Losing body fat could reduce the size of your breasts or hips, and make the bones of your face more defined.
  • If you have a metabolic condition like hypothyroidism, that could make it harder to lose weight via dieting.
  • If you have an eating disorder or body dysmorphia, dieting might exacerbate these conditions.

Are there other options?

Exercising will help you lose body fat and gain muscle definition.

If other methods fail, weight loss can be achieved via surgery. However, these are all major operations with significant risks and side effects, and the NHS will only fund this kind of surgery for people who have tried and failed to lose weight by other methods. You can learn more about these surgeries on the NHS website.

How do I diet?

Weight loss can be confusing because there are many different types diets promoted by many different organisations.

While there are many diets that suggest changing the amount of carbohydrate (“carbs”), protein, or fat in your diet or cutting out certain foods, there currently isn’t any clear medical evidence for any of these diets being better than just reducing calories 1. Given this, the current recommendations in the UK 2 and elsewhere 3 are to reduce your calorie intake while ensuring you are doing regular exercise.

So that you are confident that your hard work will be successful, you may wish to use the diet recommended by the NHS and the British Dietic Association and available on the NHS website.

It is worth talking to your GP about weight loss, as they may be able to refer you to local NHS services for managing weight loss and your lifestyle.


  1. 1.
    Sacks, Frank M, Bray, George A, Carey, Vincent J, Smith, Steven R, et al. (2009) “Comparison of weight-loss diets with different compositions of fat, protein, and carbohydrates.” N Engl J Med, 2009(360), pp. 859–873. Link
  2. 2.
    National Institute for Clinical Excellence (2014) “Obesity: identification, assessment and management (CG189).” Link
  3. 3.
    Jensen, Michael D, Ryan, Donna H, Apovian, Caroline M, Ard, Jamy D, et al. (2014) “2013 AHA/ACC/TOS Guideline for the Management of Overweight and Obesity in Adults.” Circulation, 129(25 suppl 2), pp. S102–S138. Link

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