PHOTO CREDIT: Jacques Marais

With the large amounts of popular “diets” available, the metabolic diet is currently in the spotlight. But what is it and what do the experts say about it, especially for the active trail runner?

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What is the metabolic diet?

The metabolic diet is a high fat, high protein, low carb diet with a carbohydrate reload period during the weekend. The rationale behind this is that when the body is restricted from carbohydrates, it causes the body to go into a state of “ketotosis”. This happens when there is not enough glucose (glycogen) in the cells, so the body looks for other resources for energy and often uses fatty acids as an alternative fuel source.

The theory behind this is that the commonly used energy source, glucose, is no longer available. The body reacts by dropping the production of insulin and increasing the production of glucagon. Glucagon tells the body to make more glucose from stored fat and muscle. (This means that fat may be used for energy, but so is muscle…) However this is a longer process and the cells are slow to react – this results in a lethargic feeling and a lack of energy.

In the metabolic diet (compared to the Atkins diet) this total lack of glucagon is countered by consuming carbs for 2 days in a week (weekends) to reload the muscles and liver with glycogen.

The dietician’s opinion

In theory the diet sounds sensible, as fat is used for energy. However, so is muscle, which means that muscle tissue breakdown is going to happen and probably also the reason for losing kilograms on the scale (muscle weights more than fat). The metabolic diet tries to overcome this by consuming carbs (any carbs) over weekends… For any person, especially the runner, this is not ideal.

Firstly, you may lose muscle mass, which is counterproductive as an athlete.

Secondly, there will be a lethargic feeling joining the low carb diet during the week, which is counterproductive to your training program. You would like to be able to put everything into your training in order for adaptation to happen i.e. gaining muscle, getting fitter, enduring better. This cannot happen if there is no energy to train with.


The expert’s recommendation is a healthy, balanced diet on a daily basis. That will mean that you consume protein, low GI complex carbohydrates and healthy fats in every meal, every day. Weight loss/fat loss will only happen when energy out exceeds energy in. That is simple physics and law of nature.

Best carbohydrate options are low GI carbs e.g. low GI bread, provitas, large flake oats, fruit, vegetables.

Best protein sources include high quality protein from meat, fish, chicken without fat, eggs, low fat cheese. Other protein sources include nuts, seeds, quinoa, tofu, lentils, beans.

Fat choices should be plant based e.g. avocado, nuts, olives and olive oil etc.

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