The acute 1-week effects of the Zone diet on body composition, blood lipid levels, and performance in recreational endurance athletes.

Department of Life Sciences, Kingston University, Kingston KT1 2EE, England.
The Journal of Strength and Conditioning Research (Impact Factor: 1.86). 03/2002; 16(1):50-7. DOI: 10.1519/00124278-200202000-00009
Source: PubMed

ABSTRACT The aim of this study was to examine the effects of a 7-day Zone diet compared with a normal diet on maximal oxygen uptake (V(O)2 max), running time to exhaustion during endurance performance, and body composition. Eight men, with the following physical characteristics (mean +/- SE), participated in this study: age, 26.1 +/- 1.9 years; height, 178 +/- 1.7 cm; mass, 70.7 +/- 2.1 kg; and V(O)2 max, 54.6 +/- 3.1 ml x kg(-1) x min(-1). All subjects undertook pretesting for V(O)2 max, time to exhaustion (80% V(O)2 max), and body composition (Biostat 1500) before following either the normal diet or the Zone diet for 7 days. These performance trials were performed before and after the dietary period. There was a significant (p < 0.05) decrease in total energy consumption from a mean of 2,314 +/- 334 kcal on a pretest diet to 1,994 +/- 438 kcal on the Zone diet. Subjects showed a significant reduction (p < 0.02) in body mass from 70.7 +/- 2.1 kg to 69.8 +/- 2.1 kg. In the 80% V(O)2 max time to exhaustion trial, there was a significant reduction (p < 0.05) in time to exhaustion from 37.68 +/- 8.6 minutes for the pretest diet to 34.11 +/- 7.01 minutes for the Zone diet. In conclusion, the claim of the authors of the Zone diet that performance time and V(O)2 max can be improved was not shown in this 1-week research trial. We would suggest that this is not a nutritional strategy that athletes should use until further work has been conducted.