Low Carbohydrate - How Do Low Carb Diets Work?

Reviewed by Dietitian, Juliette Kellow BSc RD

Low carb diets, like the Atkin's diet have been around for a long time. Do they work? Are they safe? Read dietitian, Juliette Kellow's verdict on low carbohydrate diets.

Well Known Low Carb Diets

As well as the Atkin's diet, low carbohydrate is the basis for a number of diet plans, the list below shows some of the more well-known versions. The different types do have minor variations but all are basically low carb diets.

• The Atkin's Diet - probably the most famous, by Dr Robert Atkins
• High Protein Diet
• Stillman Diet
• Scarsdale Diet
• Hollywood Diet
• Ketogenic Diet
• Zone Diet
• Dukan Diet
• Go Lower

What Are Low Carb Diets?

Low carb diets are based on the premise that a diet very low in carbohydrate leads to a reduction in the body's insulin production, resulting in fat and protein (muscle) stores being used as its main energy source.

The aim of low carbohydrate diets is to force the body to use fat as its main energy source, when this happens a person produces 'ketone bodies' to fuel parts of the body that can not use fat as an energy source - the brain, and red blood cells, in particular. When this happens a person is said to be in a state of ketosis - characterised by smelly breath (an acetone smell like nail varnish) and side effects such as nausea and fatigue.  

What's Involved?

Basically you cut out virtually all carbohydrate from your diet and increase your protein and fat intake. So you cut out things like pasta, bread, rice and alcohol, yet you eat unlimited amounts of meat, cheese and butter. That's why the Atkin's diet claims to be so luxurious.

Do Low Carbohydrate Diets Work?

In the short term, most people who go on low carb diets do lose weight and they lose it very quickly. However, the majority of weight loss comes from loss of water and muscle tissue, not fat which is what you need to lose to keep the weight off. Also, if you're trying to lose weight permanently, losing precious lean muscle tissue is like sabotaging your own body. Muscle tissue is metabolically active, and burns calories even when you are at rest. A decrease in the amount of muscle tissue you have will lead to a decrease in the number of calories you need each day to maintain your weight, making it much harder to keep your weight under control when you stop following the low carb diet.

So Why Do It?

People are attracted to low carb diets as weight loss is very rapid, and we like to see instant results on the scales! Lots of Hollywood stars go on low carb diets because they need to drop a dress size for a film - they don't do it for permanent weight loss or good health.

Is Low Carb A Healthy Diet?

In a word, no! Essential vitamins and nutrients come from a balanced diet and low carbohydrate diets are certainly not balanced. You can only get many essential nutrients from fruit, vegetables and grains - low carb diets only allow very small amounts of fruit and veg - definitely not enough to give you your recommended daily allowance. The Atkin's diet claims to clear up all manner of ailments, but the bottom line is these diets are lacking in nutrients essential for good health and the high level of protein puts a huge strain on your kidneys.

Low carb diets are also likely to encourage yo-yo dieting, cycles of losing and regaining weight, which has been shown to be a health risk.

Dietitian Says:

"Diets that recommend we cut back on starchy carbohydrate are an 'in vogue' means of losing weight and have gained a lot of attention in the media. However these diets could actually be harming our health in the longer term. The American Heart Association have expressed concern that their high fat content, particularly saturated fat, increases the risk of heart disease in those who follow these diets long term. Low carbohydrate diets go against all the current healthy eating principles and are deficient in many vitamins, minerals and dietary fibre, as they restrict the intake of fruit and vegetables. There are also concerns that these diets, if followed long-term, may increase the risk of kidney, bone and liver problems.

A balanced, healthy diet combined with exercise is still the most effective and safe long-term way to lose weight. However the results are gradual and require perseverance. Quick fixes such as the Atkins diet do not hold up to scrutiny and at present there are no long-term studies on the safety or efficacy of these diets."