Updated 08 October 2015

The 10 worst diet myths

You've all heard them: dieting is easy. Just cut out fats and carbs, eat lots of popcorn and drink lots of fruit juice. Welcome to the Land of Diet Myths.


Annchen Weideman, consultant dietician at the Vincent Pallotti Hospital in Cape Town, gives us the lowdown on the 10 worst diet myths:

1. Drink lots of fruit juice, as long as it’s pure

Fruit juice is concentrated, dissolved fructose (70%) and glucose (30%). The average 200ml pure juice contains approximately six fruits. The human body copes well with small amounts of fructose and glucose from eating single servings of fresh fruit, where the pulp slows down rapid absorption of these simple sugars. Juices place a burden on the body to produce insulin in an effort to cope with large amounts of quickly absorbable sugars. In other words, eat your fruit, don’t drink it.

2. Fat free is the only way to diet

Health authorities have recommended "low-fat" or "fat-free" diets for almost four decades. The reasoning was that fat contains more kilojoules (38kJ per gram) than either carbohydrates or protein, containing 17kJ per gram.

It makes mathematical sense that if you eat equal quantities of these nutrients, fat will be most fattening. But this equation discounts several important facts: fat offers the highest satiety value, and severely restricting it from your diet will lead to incessant hunger, and also make it a lot more difficult to stick to any diet.

The second discounted point is the GI-lowering effect of fat with meals, and thirdly, the life-saving anti-inflammatory properties of omega-3 fats. By restricting all fats, we've probably increased our exposure to inflammatory conditions such as heart disease, abdominal obesity, hypertension, diabetes and certain cancers.

3. Base your meals on cereals and starches

The Food Guide Pyramid has indeed become our tombstone. Many years of starchy eating (6 – 11 portions per day, as recommended) have fuelled our abdominal fat stores. This could lead to an increased production of insulin in response to chronic, large amounts of blood-sugar release from starches.

Fresh fruit and vegetables are a healthier alternative to starchy eating, since their biochemistry call for less insulin release. Fresh fruit and vegetables should be used to substitute half of our starches. No diet based on starch will promote or sustain weight loss.

4. Jelly babies and marshmallows are fat-free, and not fattening

The food industry knows you confuse fats and sugars, and exploits this. If you think you can regularly, safely indulge in a packet of "fat-free" jelly babies while you're trying to lose weight, you've fallen in the trap. These products might be fat-free, but contain concentrated sugar, with a high insulin-stimulating action. High insulin release is exactly what you want to avoid if you want lasting success with weight loss.

5. Eat at least five fruits daily

This recommendation assumes that these five fruits will substitute extras in your diet, such as starches or desserts. It's no use eating your daily junk diet, plus five fruits to soothe your conscience. Then even fruit is fattening.

6. Avocado is fattening

This healthy fruit has been unfairly blamed as fattening for too long. Fruit is generally fat-free, and the fat in avocado is not "high-fat", "bad fat" or even fattening. Also – it has no effect on your cholesterol or blood-sugar levels.

7. It's what you eat – when is not important

We often skimp on our food intake during the day, with the result that by late afternoon our need for blood-sugar replenishment overrides all reason. One of the main purposes of breakfast is to get a solid, slow supply of blood sugar going. Topped up by a sensible lunch and late-afternoon snack, your supper should be smallest of your meals.

Breakfast has 16 – 18 hours to metabolise, lunch has 10 – 12 hours, and supper usually has two or three hours before we expect our sleeping bodies to cope with the digestion of the largest meal of the day. That's why we should "breakfast like a king and supper like a pauper".

8. Apple cider vinegar breaks down fats

The only thing apple cider vinegar breaks down is the lining of your stomach. It will not make you thin, and what’s more, it could cause stomach ulcers if the vinegar is taken on a regular basis.

9. Breakfast cereal and breakfast bars will make you thin

If you want to kick-start your insulin production to put your body in effective fat storage mode, try doing this. Having high-GI starch as your meals, plus bars loaded with sugars, harmful fats and more refined starch in between, will make sure that you become a yo-yo dieter. Be prepared to be a lot worse off than you were when you started this ridiculous diet.

10. Cream crackers, rice cakes and popcorn are 'free foods'

Firstly, the need for free foods means that your diet has little satiety value, or you're stimulating glucose and insulin spikes in a self-perpetuating cycle by means of bad eating habits.

Secondly, no refined starch-based foods are "free". The term "free" refers to the low-kilojoule content of these foods, but by frequently eating "free" starches, you're stimulating insulin production, and again, putting your body in good fat-storage mode. This has little to do with kilojoules.

Read more:

Nutrition basics in a nutshell
25 tips for a healthier, slimmer shape
Are you ready to lose weight?


5 reasons to love avocados

2018-10-14 07:00

Read Health24’s Comments Policy

Comment on this story
Comments have been closed for this article.

Live healthier

Smoking dangers »

Hubbly hooking lots of young adults on tobacco Hookah smokers are inhaling benzene Many young adults misinformed about hookahs

Hookah pipes far from harmless, study warns

In addition to toxic substances from tobacco and nicotine, hookah smoke exposes users to charcoal combustion products, including large amounts of carbon monoxide.

Managing incontinence »

5 avoidable triggers that can make urinary incontinence worse

Urinary incontinence is a manageable condition – here are a few common triggers of urinary leakage.