1. Potatoes make you fat – false
It was once thought that the key to weight loss was eliminating all high-carbohydrate foods, including pasta, rice and potatoes. We now know that carbohydrates are the body's preferred energy source. Eating a potato, or any type of carbohydrate rich food, won't automatically make you fatter.
However, if you are watching your weight, enjoy potatoes in moderate quantities and be careful of how you eat them (for example, butter and sour cream are high in fats. Reduced-fat natural yoghurt is a healthier choice).
You have to regularly eat more energy than your body needs to put on weight. This is harder to do with high-carbohydrate foods than high-fat foods, because carbohydrates contain about half the amount of energy compared with fat. When choosing high-carbohydrate foods such as grains and cereals, wholegrain options are best.
2. Single food diets really work – false
There are plenty of diets based on the belief that the digestive system can't tackle a combination of foods or nutrients. Commonly, carbohydrates (such as grain foods) and proteins (such as meat foods) are said to 'clash', leading to digestive problems and weight gain. The opposite is often true. Foods eaten together can help the digestive system. For example, vitamin C in orange juice can increase iron absorption from a meal rich in plant-based iron like beans and rice, lentils and other legumes.
Very few foods are purely carbohydrate or purely protein; most are a mixture of both. The digestive system contains enzymes that are perfectly capable of breaking down all the foods we eat. Single food diets should be avoided.
3. Breakfast should consist of fruit only – false
There is no evidence that eating only fruit at breakfast has any health or weight loss benefits. Most fruits are not very high in complex carbohydrates, which the body needs for fuel after an all-night fast. They are, however, a good source of fibre and vitamins.
Cereal foods (especially wholegrain varieties) like bread, muffins and breakfast cereals are a much better source of carbohydrates to get you going in the morning. You can add fruit to your breakfast for additional nutrients and taste.
4. There are some magical foods that cause weight loss – false
Some foods, such as grapefruit or kelp, are said to burn off body fat. This is not true. Dietary fibre comes closest to fulfilling this wish, because it provides a feeling of 'fullness' with minimal kilojoules. High-fibre foods such as fruit, vegetables, wholegrain breads and cereals, and legumes also tend to be low in fat.
5. Drinking while you are eating is fattening – false
The theory behind this misconception is that digestive juices and enzymes will be diluted by the fluid, and this will slow down the digestion and lead to excess body fat. There is no scientific evidence to back this up.
In fact, evidence suggests that drinking water with your meal improves digestion. Kilojoule-heavy drinks such as alcoholic beverages can be fattening if consumed in excess, but drinking them with meals doesn't make them more fattening.