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Calvin and Low Carbs

LOW CARB DIETS: Are they effective or just the flavour of the month?

Few issues in health are as controversial as food, what we do eat and what we should be eating.  The current trend for low carbohydrate diets, often combined with a high fat intake, the so called “paleo diet” is of concern to many healthcare professionals, doctors and dieticians alike. Some people do lose weight on this diet and sing its praises, but what is the evidence to recommend it.  The opinions are sometimes firmer than the evidence!


Carbohydrates (starch) have traditionally formed the foundation of our diets for centuries so why pick on them now?  Carbs provide fuel for energy and are the main fuel for the brain, that’s why it is difficult to teach anyone who is hungry. Indications are that the global obesity epidemic (up to 50% of South Africans are overweight or obese) is linked to the availability of cheap refined starches and fats—the “MacDonald’s and Coke” diet. Together with a high intake of refined starch like white bread and sugars, many people’s lifestyles are less physically active and the resulting energy imbalance leads to weight gain.

According to Claire McMahon a consultant dietician based in Claremont, Cape Town, a moderate carb diet is about 130 grams of carbohydrate a day and this is the minimum recommended (by the WHO) daily allowance for an adult. Below this level you brain will battle to get enough energy. There is evidence that the depression experienced by anorexics is partly due to low blood glucose levels.

A 15 gram portion of carb includes a slice of bread or half a cup of rice, pasta or cereal. A serving of fruit (a tennis ball size) also contains 15 g of carbohydrate. Green vegetable contains about 5 grams per portion, pumpkin, butternut and peas about 7 grams a portion.

Low Carb diets, where the carbs are replaced by fats or protein, have not been shown to be better than a low calorie balanced diet for long term weight loss. The additional metabolic load of a high protein diet may be harmful to some and high intake of animal fats may increase the risk of heart disease in the long term.

Claire recommends that rather than restricting carbs one should have them in their most natural form (Low G.I.) such as whole wheat or multigrain bread, oats, brown rice and high fibre foods and restrict refined carbs like white bread and sugars. The bulk of the carbs should be taken at breakfast time with less at supper.  Low GI carbs in the mornings will digest slowly and help fuel your day.  Claire also recommends restricting the intake of (often hidden) refined carbs in processed foods like breakfast cereals, energy bars, healthbars, fruit juices and fruit itself.  All fruit contains sugar and two servings daily is sufficient. A better source of micro nutrients like vitamins is green vegetables that have much lower sugar content.

If you have specific concerns about your or your families diet Claire McMahon can be contacted on 021 6834858.