NUTRITION
Fad diets – beware low carbohydrate regimes Gillian Woodward It is that time of year again when you take off a few layers of winter clothing to expose your white flesh to the milder conditions. Are you disappointed that about the amount of extra flab hanging over the belt of your summer jeans? I hope you are not going to embark on one of the many fad diets that have pervaded the media, especially women’s magazines, in recent months.
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ne of the worst for athletes in training, or anyone who is active for that matter, has to be the high protein, low carbohydrate diet. Call it what you like – Atkins Diet Revolution, Sugar Busters, Scarsdale, Protein Power, Slim Forever – they all promote the same theme. Eat as much protein and fat as you can, but avoid carbohydrates at all costs.
We need carbohydrates
To a sports dietitian or exercise physiologist, this avoidance of carbohydrate goes completely against the grain. After all, carbohydrate is our major supply of readily available energy, being stored in the liver and muscles as glycogen. When these stores are depleted, we feel lethargic, fatigued and generally unable to exercise with the usual power. Our bodies need at least 100 g of carbohydrate per day (and much more if we are active) to stop us burning more valuable nutrients for a supply of glucose (like muscle protein). But athletes who train for an hour or two a day, need much more than this – more like 5-8 grams of carbohydrate per kilogram of body weight. For a 70 kg athlete, that amounts to at least 350-560 grams per day! A far cry from the 20-90 grams per day promoted by many of the high protein, low carbohydrate diets.
Side effects
Side effects of long term high protein diets can include fatigue, headaches, bad breath, loss of lean body mass (muscle tissue), constipation, nausea and ketosis. Losing muscle mass puts you at a particular disadvantage, as muscle burns energy at a much greater rate than fat. This is why when you go back to eating a more balanced diet, you can gain weight easily, because you now have a lower muscle to fat ratio. If you do embark on a low carbohydrate diet, you are instructed to avoid or at least severely restrict most of the basic food groups. All bread and cereals, biscuits, pastas, rice, fruit, starchy vegetables (potato, corn, pumpkin, peas), legumes, milk, yoghurt and soymilk products are off limits. Also of course there would be no sugar, jam, honey, fruit juices, sports drinks or soft drinks of any kind allowed. You are left with only meat, eggs, fats (butter, cream, margarine, oil), tea, coffee (without the milk or sugar of course) and some alcoholic drinks like wine and spirits. A few non-starchy vegetables like leafy greens, tomato, broccoli and cauliflower are also allowed. How boring, you might say! Even most of the fats are useless to you on this diet, as there is no bread or biscuits to put them on and no potatoes to fry in them!
30 THE AUSTRALIAN ORIENTEER SEPTEMBER 2004
You are so restricted in the foods allowed to be eaten, that you eat less overall for the day, ending up in energy deficit (consuming less kilojoules or calories than your body requires). This is how all successful weight loss diets work. Certainly protein is satisfying to hunger. A large piece of rump steak or six slices of roast lamb will make you feel full. But it also provides you with excess protein that your body doesn’t need, so you have to break it down and get rid of the extra nitrogen via the kidneys, putting extra strain on them. People do report quite fast weight loss on these diets (at least initially anyway). This is understandable, because without carbohydrates coming in via the diet, you deplete all your glycogen stores. With every gram of glycogen used up, 3-4 grams of water are also released. Losing 500 grams of glycogen thus results in the bathroom scales showing a 2 kg weight loss – very exciting at first. But this rate of weight loss is not maintained. Studies on high protein diets, particularly the Atkins method, have shown that those who manage to stay on them for three months, can lose weight successfully in the short term, but at no greater rate in the long term than those on higher carbohydrate, lower fat, moderate protein weight loss regimes. The drop-out rate from high protein diets is also very high, due to the boredom/ restriction factor.
Nutritional concerns
What is more of a nutritional concern however, is the lack of certain vital nutrients on these diets. They are low in vitamins A, E, B6, folate, and thiamin. They also provide insufficient quantities of the minerals calcium and magnesium, as well as being deficient in fibre and potassium. The antioxidants and phytoestrogens are also missing. The diets are low in plant products which have been consistently shown to reduce risk of diseases like diabetes, heart disease, stroke, cancer, osteoporosis and bowel disease. It is well known from research that after heavy exercise athletes can experience temporarily depressed immunity. Scientists refer to this as post exercise immunosuppression or PEIS. Studies have shown that in athletes who train with low glycogen levels after being on low carbohydrate diets for several days, there is a greater release of stress hormones compared to those who have had a higher carbohydrate diet. The more stress hormones released, the lower the immune function. Consuming carbohydrates during exercise has also been shown to be beneficial in terms of reduced stress hormone release. Cyclists fed 30-60 grams of carbohydrate during two and a half hours of strenuous cycling did not show a drop in immune cells, unlike their counterparts who had no carbohydrate during the same exercise.
Carbohydrates are a valuable fuel and keep us healthy
So it seems that carbohydrates are not just important to provide a readily available fuel source to muscles, but also help to keep us healthy and avoid disease as well. So keep the carbs in your daily diet, but not in massive quantities, and avoid the ‘fast release’ or high GI and sugary foods (see article on GI in Autumn 2003 issue) if you need to shed kilograms. Base your diet on plant foods like vegetables and fruit, grainy cereals and breads. Have a little more protein rich foods if you like, but make sure they are low in (saturated) fat. Choose lean meats, skinless chicken, grilled fish and low fat milk, yoghurt, cottage or ricotta cheese as well as eggs. Make sure that your new healthy ‘summer look’ eating regime is sustainable and is accompanied by plenty of daily exercise. Then you will be on a sure path to successfully fitting into those swimmers by the height of the season, and of course be able to compete at your peak in orienteering. More specific guidelines in the December issue will help you to control your body weight in a sensible way.
