The Low Carb Disadvantage?

There are a group of diets that promote the benefits of reducing carbohydrate intake, these are often referred to as low carbohydrate or low card diets. Probably the best known of these is the Atkins Diet, devised by the late Dr Robert Atkins. Although there are other examples including the Protein Power Diet, the Scarsdale Diet and the diet for blood type O recommended by the Blood Type Diet. The theory behind all of these diets is that by reducing you carbohydrate intake to very low levels you force your body into burning its fat reserves and you lose weight as a result.

Your body normally uses glucose as fuel; this glucose comes from the carbohydrate that you eat. If you are eating a balanced diet your body should be getting all of the glucose that it needs. If you are not getting enough carbohydrate in your diet, perhaps because you are following a low carb diet plan such as Atkins, the level of ketones in blood will increase and your body will start to derive energy from stored fat; this is called ketosis.

This article mainly considers the Atkins Diet although the comments are equally true of most low carbohydrate diets. The variations between them are mainly around the phases that you go through when following the diet.

The Atkins Diet consists of four phases: Induction, Ongoing Weight Loss, Pre-maintenance and Lifetime Maintenance.

The induction phase, which must be followed for at least two weeks (although you can extend this if you want to), requires you to limit your carbohydrate intake to 20g a day; it is during this phase that your body will switch from burning carbohydrate to burning fat.

In the ongoing weight loss phase you slightly increase your daily carbohydrate intake by 5g per week until you are losing around 1 to 3lb per week. This is called your Critical Carbohydrate Level for Losing Weight and will vary from person to person.

When you have between 5 and 10lb left to lose you enter the pre-maintenance phase. In this phase you increase your daily carbohydrate intake by 10g every week until your weight loss slows down to around 1lb per week. The final phase is lifetime maintenance and aims to help you maintain your weight.

So, does it actually work? The evidence suggests that it does and, especially in the induction phase, can deliver rapid weight loss. Perhaps, a better question to ask is whether it works any better than a low fat calorie controlled diet and here there is not very much evidence from properly conducted trials. The evidence that exists suggests that low carbohydrate diets can achieve greater weight loss than an equivalent low fat, calorie controlled diet and increased the amount of HDL (good) cholesterol in the blood without increasing the overall level of cholesterol. There is also evidence to suggest that the low carbohydrate diet can cause marginal improvements in insulin resistance.

It is uncertain as to whether the claims relating to ketosis and weight loss are the whole story, as one study noted that people on low carbohydrate diets tend to naturally decrease their calorie intake; most of the permitted foods in low carbohydrate diets have a fairly low glycemic index (GI) and, generally speaking, low GI foods make you feel fuller for longer and you eat less as a result.

However, there are some quite serious drawbacks and unpleasant side effects of low carbohydrate diets. Forcing your body into ketosis can cause tiredness, weakness, dizziness, insomnia, nausea and bad breath. In the early stages of a low carbohydrate diet it is common to experience diarrhoea, although this does wear off after a while. Another possible side effect is constipation, this is a result of a lack of fibre in the diet and can be helped by using your daily carbohydrate allowance to consume vegetables containing fibre such as broccoli, asparagus and spinach.

Some health professionals have expressed serious concerns about the Atkins diet in particular in relation to its relatively high fat intake, although this does not seem to be borne out by the results in the limited studies that have taken place, where the higher proportions of fat did not seem to increase risk factors like total cholesterol or LDL (bad) cholesterol and probably improved risk factors by decreasing triglyceride levels and increasing HDL (good) cholesterol levels.

Severe ketosis over long periods can be dangerous and has been linked to liver and kidney damage, for this reason health professionals do not recommend low carbohydrate diets for anything other than short term use, generally not exceeding 14 days. Although the Atkins Diet in particular introduces more carbohydrate as you progress through the phases there have been no independent studies as to how long your body is in ketosis.

At the end of the day, the choice is a personal one. Some people can quite happily exist on a diet of protein and fat, while others find this their idea of hell.

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