Zone Diet: you can't live off just carbohydrate, protein and fat

Zone Diet Is a No-No

Athletes are always tinkering with their diets in an attempt to boost performance. Until recently carbohydrate was regarded as the main component of most athletes’ diets because, as we all know, carbohydrate is the king of fuels when it comes to athletic performance. However, the zone diet offers a radically different approach whereby carbohydrate, protein and fat are consumed in ratios of approximately 40:30:30 rather than the typically recommended 55:15:30.

The claims made by the authors of the zone diet book include loss of excess body fat, reduced hunger between meals, reduced risk of chronic disease and improved athletic performance. A UK-based research team decided to test the authors’ claim that the zone diet would increase time to exhaustion during endurance events. Eight male volunteers followed either a normal diet or the zone diet for seven days. They were subjected to a battery of tests before and after the dietary period, including assessment of body composition, maximum oxygen uptake and time to exhaustion.

The results showed that time to exhaustion during an 80% VO2max time trial fell by almost four minutes for the subjects following the zone diet. The researchers also noted a trend towards decreased VO2max, which would have significant implications for training and subsequent performance in endurance events. The long and short of it is that the research team found none of the improvements claimed by the authors of the zone diet and concluded that athletes would be well advised to steer clear of this diet if they were serious about their training and future performance in competitive events.

Journal of strength and conditioning research, vol 16 (1) 50-57

Nick Grantham

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