Zone diet

Barry Sire, PhD, author of Enter the Zone and Mastering the Zone, argues that a high-carbohydrate diet can impair athletic performance and contribute to obesity. The author believes that carbohydrates and insulin are harmful substances and recommends a complex diet that limits carbohydrate intake. Sire recommends consuming 40% of calories from carbohydrates, 30% from protein, and 30% from fat at each meal.

It is suggested that in order to achieve peak performance, athletes should follow the Zone Diet, which may promote optimal athletic performance by altering eicosanoid production so that the body produces more "good" eicosanoids than "bad" ones. Barry Sire claims that eicosanoids are the most powerful hormones and control all physiological functions.

Proponents of the Zone Diet recommend limiting carbohydrate intake to prevent the body from producing too much insulin, since high levels of insulin increase the production of "bad" eicosanoids. "Bad" eicosanoids may impair athletic performance by reducing oxygen delivery to cells, lowering blood glucose levels, and making it more difficult for the body to use carbohydrates. According to Barry Sire, insulin also:promotes obesity by causing carbohydrates to be stored as fat.

The protein in the Zone Diet is thought to increase glycogen levels and promote the production of "good" eicosanoids, counteracting the effects of insulin. These eicosanoids likely enhance endurance by increasing oxygen delivery to cells, promoting the utilization of stored fat, and maintaining blood GLUCOSE levels.

Such information, presented in scientific language, should frighten athletes. However, the scientific basis of such a diet can be completely criticized. Eicosanoids do not cause diseases - they are biologically active, hormone-like compounds known as prostaglandins, thromboxanes and -eukotrienes. Eicosanoids participate in the regulation of inflammation, coagulation reactions and the activity of the immune system. The assertion that eicosanoids are all-powerful is unfounded, the physiology of the body is not so simple. In addition, there is no evidence that insulin produces "bad" eicosanoids, and glucagon - "good". The literature on nutrition and biochemistry does not contain information on metabolic pathways linking diet, insulin, glucagon and eicosanoids. The idea that this diet (or any other) completely regulates insulin and glucagon production is not supported endocrinologically, and "the claim that insulin and glucagon control eicosanoid production is not supported biochemically. Finally, the idea that eicosanoids control all physiological functions (including athletic performance) is not only unfounded, but also oversimplifies complex physiological processes.

Athletes need carbohydrates to maintain high levels of performance. Contrary to what the Zone Books claim, consuming a high-carbohydrate meal 1-4 hours before exercise improves performance by increasing blood glucose levels and replenishing glycogen stores. Consuming carbohydrates during one-hour or longer exercise improves endurance by providing glucose to the muscles when muscle glycogen stores are depleted. Consuming carbohydrates immediately after a vigorous workout increases muscle glycogen stores.

Body weight is determined by how many calories are consumed compared to how many are "burned." There is also no evidence that insulin is the cause of obesity in humans.

The Zone Diet is simply low energy. The Zone books try to disguise this by having people count protein and carbohydrate components instead of kilocalories. Although Seere does not emphasize energy intake, the Zone Diet provides only about 1,200 calories (120 grams of carbohydrate) for the average woman and 1,700 calories per day (170 grams of carbohydrate) for the average man. The diet is also deficient in thiamin, pyridoxine, magnesium, copper, and chromium.

The Zone Diet does not increase the ability to "burn" fat during exercise. The best way for athletes to increase their ability to "burn" fat is to continue to train. As for gradual fat loss, this occurs as a result of physical exercise, when more kilocalories are "burned" than are consumed with food, and not from a special diet.

Dangers of the Zone Diet:

• Inadequacy of kilocalories (approximately 1700 for men and 1200 for women)
• Inadequate amount of dietary carbohydrates (approximately 170 g for men and 120 g for women)
• Inadequacy of nutritional elements (thiamine, pyridoxine, magnesium, copper and chromium)
• The misconception that the zone diet will improve performance

Finally, athletes cannot train or compete for long periods of time on such a low-energy, low-carbohydrate diet. Athletes require adequate calories and carbohydrates to maintain muscle glycogen stores. Those following the Zone Diet will end up on the edge of starvation and poor performance.