Can diet foods hurt you?

The weight-loss industry is worth millions. It's hardly surprising that there are hundreds of specially formulated diet foods on the market.

Most of these foods promise they're either low in energy or sugar. But are they really slimming? Are they safe?

There are six main factors to consider:

1) High fat content

Many foods marketed at slimmers or diabetics, do indeed have low sugar, but have such a high energy and fat content that there's no way that they're going to help you lose weight.

On a recent visit to the supermarket, I checked out the composition of one of the most popular brands of diet chocolate. The manufacturers would like you to believe that these products will help you lose weight.

I was surprised to see that the "slimming" chocolate has practically the same energy value as regular milk chocolate, namely 2038 kJ/100g; and that it contains more total fat (39g/100g) and more saturated fat (20g) than standard milk chocolate (see below)!


Chocolate Energy / 100g Carbohydrate / 100g Total fat / 100g Saturated fat / 100g
Slimming 2038 kJ 30g 39g 20g
Regular 2240 kJ 60g 30,6g 18g

Although this popular “slimming chocolate” contains 50% less carbohydrate, it's higher in fat and saturated fat than standard chocolate, and every gram of fat provides 37 kJ of energy.

High intakes of total fat and saturated fat are something slimmers should avoid, and they are also harmful in terms of heart health. They’re also linked to certain types of cancer.

2) High sorbitol / sugar alcohol content

Manufacturers of foods intended for slimmers or diabetics often use compounds called sugar alcohols (e.g. sorbitol) to replace sugar in their products.

Unfortunately, sugar alcohols have a strong laxative effect. Always check diet foods for sorbitol, mannitol, lactilol, xylitol or maltitol, all of which, when eaten in excess, cause bloating, abdominal pain and diarrhoea. Any product that contains more than 5g of sugar alcohol per serving should mention the laxative effect of this ingredient.

3) High fructose content

Another ploy that food manufacturers use so that they can state "sucrose-free" on their labels, and thus lure slimmers, is to substitute fructose for sucrose in the product's composition.

Fructose has the same energy value as sucrose, and there are indications that excessive intakes of fructose can cause diarrhoea in susceptible individuals. It has also been linked to eye damage (retinopathy), and research indicates that it could actually be more fattening than sucrose.

The fact that excessive fructose intake may cause damage to the retina of the eye has prompted the recommendation that people should not have more than 20g per day.

4) High energy content

Many slimming shakes or meal-replacement products have a very high energy content. A quick check of some of the most popular brands showed that some contained more than 2100 kJ per serving. No wonder DietDoc forum users complain they aren't losing weight on this type of shake.

Before you buy a slimming shake or a meal-replacement product, check that the product contains less than 2100 kJ (500 calories) per serving, otherwise you won't lose any weight.

5) High vitamin and mineral content

Some diet foods also contain very high doses of added vitamins and minerals.

Basically, an ideal shake or meal replacement should only provide you with one third of your daily requirement for vitamins and minerals. After all, you're going to eat two other balanced meals per day which will also contain vitamins and minerals.

Most slimmers also take additional multivitamin and mineral supplements. Before you know it, you'll be drowning in an excess of vitamins and minerals. Excessive intake of beta-carotene, as well as vitamin A and E, has been linked to a number of health problems.

When you're trying to lose weight, be careful not to overdose on too many vitamins and minerals – in the long run, this could cause more harm than good.

6) Added appetite suppressants

Diet shakes and meal replacements may also contain compounds such as synephrine or bitter orange extract to suppress the appetite. These can be highly addictive, so be careful.

They can also cause tremors, insomnia, palpitations, irritability, psychotic reactions, and other negative side-effects. A meal replacement should be just that, and not contain additives that can get you hooked.

On balance, then

When you purchase diet foods. Check that foods:

  • aren't loaded with fat and saturated fat;
  • aren't so high in energy that they counteract your efforts;
  • don't contain sugar alcohols and/or fructose at levels that can cause chronic diarrhoea or eye damage;
  • or such mega-doses of vitamins and minerals that they are potentially harmful to your health;
  • or appetite suppressants that can have negative side-effects, including addiction.

Instead, stick to a balanced, low-fat diet consisting of everyday foods – they cost less, usually taste better, are less monotonous, and are not potentially harmful. - (written by Dr IV van Heerden, DietDoc)

- (Health24, updated July 2011)

Read more:

Slideshow: Top 10 foods with hidden fats
An 18-step plan for healthy eating
The ultimate slimming guide

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