More than 40 per cent of women have eliminated specific foods from their diet over the last five years, according to the Grain Information Service. But is cutting out a food group really the passport to better health and eternal slimness? Done without careful planning, there's much that can go wrong, so read our essential guide...

Low carbohydrate diets are lower calorie and tend to have a high content of protein, which is stomach-filling and satisfying.

What can go wrong?

If you cut out too much carbohydrate, you may find your energy flagging. Your cholesterol levels can rise and too much protein may put a strain on the kidneys, too.

Keep safe

Halve your carbohydrate portions, rather than cut them out altogether, and go for the whole-grain type, which are slower releasing, filling you up for longer. Also have lots of vegetables, salad or fruit.

Click here for our guide to the GI diet

Why do it?

About five per cent of the British population is intolerant to lactose - the sugar in milk. Symptoms include bloating, nausea, stomach cramps and wind.

What can go wrong?

Dairy is one of the best sources of calcium, so cutting it out can put you at increased risk of osteoporosis. Diets rich in dairy also seem to protect against abdominal weight gain, so cutting out milk may mean you put weight on instead of losing it.

Keep safe

Even if milk is a problem for you, there are grades of intolerance, and by keeping your system challenged with a small amount of dairy every day, you may be able to keep it in your diet. Your GP can give you a breath test to ascertain how lactose intolerant you are, if at all. If you have to cut milk out completely, be sure to have calcium-fortified substitutes, such as soya milk, nuts, broccoli and canned salmon.

Click here for our guide to healthy dairy-free alternatives

Why do it?

Some level of wheat intolerance may affect around ten per cent of the population, according to Professor Jonathan Brostoff, co-author of 'The Allergy Bible' (Quadrille, £9.99). But only one per cent of people have coeliac disease - an intolerance to the gluten in wheat, rye or barley.

What can go wrong?

Wholegrain foods, such as wholemeal bread and wholemeal pasta, are among the best sources of fibre - so if you cut them out, you could find yourself feeling sluggish and constipated. Wheat is also a good source of carbs, antioxidants and energy-releasing B vitamins, so it could be harmful to cut them out without a good reason.

Keep safe

You could try cutting out wheat and gluten for a week or two. If you feel markedly better, it's something worth exploring with the help of a dietitian. If your GP won't refer you, visit www.dietitiansunlimited.co.uk for a list of private professionals. If you go it alone, replace wheat with other nutritious grains such as rice, corn, quinoa, millet and buckwheat.

Click here for our guide to healthy wheat-free alternatives 

Why do it?

Fat has nine calories per gram, which is more than in protein, carbs or alcohol.

What can go wrong?

Really low-fat diets are linked to depression. Your skin will suffer too, becoming dry. Fat is needed for sex hormone production, too; if you cut your intake too low, your fertility and even libido could suffer.

Do it safely

Just cut down on fat rather than attempting to cut it out altogether, and shift the balance of fats you do have so you're having more unsaturated fats in olive oil dressings, nuts, seeds, avocados and oily fish. The absolute minimum amount of fat you should have every day is around 25g.

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