CARBOHYDRATES

Weight loss and carbohydrates

Carbohydrates are the only fuel source for many vital organs, including the brain, central nervous system and kidneys. The digestive system breaks down carbohydrates into glucose and the pancreas secretes a hormone called insulin to help the glucose move from the blood into the cells.

Very low carbohydrate diets
Very low carbohydrate diets are becoming popular again. These diets often contain less than 60g of carbohydrate per day. Many health professionals do not support these diets because they have a high fat content (particularly saturated fat) and restrict fruit, vegetables and high fibre breads and cereals.

Low carb diets restrict healthy food choices
Advocates of very low carbohydrate diets advise people to consume kilojoules mainly from protein and fat sources. This means limiting cereals, some vegetables and fruit, while eating more meat, dairy foods and fat. Typical foods eaten on a low carbohydrate diet include beef, chicken, bacon, fish, eggs and non-starchy vegetables, as well as fats such as oils, butter and mayonnaise. Forbidden foods include fruit, bread, grains, starchy vegetables and dairy products other than cheese, cream or butter.

Very low carbohydrate diets do not meet your daily nutritional needs. To be healthy, your daily diet should include at least:

Four serves of bread or cereals
Two serves of fruit
Five serves of vegetables
Two cups of milk.
The long term safety of a diet very low in carbohydrates but high in saturated fat is still uncertain. Some experts believe it’s a recipe for a heart attack. Follow-up studies are needed over years to determine the safety of very low carbohydrate diets.

Weight gain comes from eating too many calories
The basic principle of any low carbohydrate diet is that carbohydrates cause weight gain. This is misleading. You gain weight if you consume too many kilojoules (or calories) – it doesn’t matter whether they are from carbohydrates, proteins or fats.

There’s nothing special about a low carbohydrate diet
Low carbohydrate diets cause you to lose weight because they restrict kilojoules or energy. This approach to eating starves the body of the nutrients it needs and can cause major metabolic disturbances to the body. There is nothing special about the proportions of protein to carbohydrate – there are just fewer kilojoules consumed in these diets, which causes the weight loss.

Low carb weight loss is mainly water in the short term
The body stores excess glucose as glycogen and converts glycogen back into glucose to use as fuel if there is not enough carbohydrate in the diet. Around 3g of water is needed to release one gram of glycogen, so the rapid initial weight loss on a low carbohydrate diet is mostly water, not body fat.

When a normal diet is resumed, some muscle tissue is rebuilt, water is restored and weight quickly returns, mostly as fat. This can contribute to the problem effect of dieting called the ‘yoyo’ effect.

Weight loss needs a healthy approach
A diet high in fruits and vegetables, wholegrains, legumes and low fat dairy products, and moderate in fat and kilojoules, is the best way to lose weight and keep it off.

Vegetarians and people who consume predominantly plant-based diets are generally slimmer and have much lower rates of obesity, heart disease and cancer than people who eat meat-based diets. This supports current thinking that diets high in unrefined carbohydrates help to prevent overweight and obesity.