Straight talk about the Zone diet...
The Zone diet is the latest nutrition strategy that promises to improve
athletic performance, reduce body fat and increase muscle mass. It recommends
consuming 40% of your daily caloric intake in the form of carbohydrate,
30% as protein, with fat making up the other 30%.
The Zone diet
Despite its popularity, there is little evidence that the recommendations
made in The Zone Diet can improve athletic performance. However,
it is essentially a restricted calorie diet. For individuals wanting
to lose body fat, there is no reason why the Zone diet would not prove
effective.
This type of diet is nothing new. In fact, the Greek long-distance runner
Stymphalos claimed that a meat based diet (rather than the vegetarian
diet popular with most Greek Olympians) was responsible for his Olympic
victories in the fifth century BC [2].
The Zone diet is based primarily on protein intake. Dr Barry Sears,
the author of The Zone Diet, suggests consuming between 0.8
and 1.0 gram of protein per pound of lean body mass. For a hypothetical
individual weighing 180 pounds, with a body fat percentage of 12%, daily
protein intake would work out between 127 grams and 158 grams per day.
Because protein should represent 30% of daily caloric intake, daily
fat consumption would be 70 grams, with carbohydrate intake at 211 grams.
The daily energy requirement of the Zone diet for a 180 pound individual
works out at approximately 2106 calories.
According to Dr Sears, this dietary regimen results in a greater delivery
of oxygen to the working muscles, a condition known as "the Zone".
However, Dr Sears has come in for a good deal of criticism from exercise
scientists, mainly because the Zone diet directly challenges several
long-standing assumptions.
Performance
Firstly, the Zone diet suggests a daily carbohydrate intake comprising
40% of total energy consumption. For a male weighing 180 pounds, this
represents 211 grams of carbohydrate per day. Such a recommendation is
in sharp contrast to the majority of scientific research, which shows
that carbohydrate is essential for regular physical activity.
For example, a recent study compared the effects of different levels
of carbohydrate intake on the performance of two Swedish ice hockey teams
[1].
Both teams took part in two games separated by three days. During this
three-day gap, the players were assigned to one of two groups. The first
group consumed a normal mixed diet that provided around 40% of energy
from carbohydrate. Group two had their diet supplemented with extra carbohydrate.
Energy from carbohydrate in the second group represented 60% of total
energy intake.
The study clearly showed an improvement in physical performance in the
high carbohydrate group. Simply put, a diet containing only 40% of its
calories from carbohydrate was insufficient to meet the energy needs
of elite athletes.
Protein
The Zone diets' recommendations for daily protein intake are a little
closer to the mark. The amount of protein required by those participating
in regular exercise sessions remains a topic of considerable debate.
Nevertheless, there is research to show that both endurance and strength
exercise increase protein requirements.
For example, Dr. Peter Lemon and a team of researchers from Kent State
University, Ohio, and McMaster University, Ontario, studied a group of
12 male subjects during two months of resistance training [3]. They found
that a protein intake of 81 grams per day (1 gram per kilogram of bodyweight
for a 180-pound male) results in a negative nitrogen balance.
Nitrogen balance is a measure of protein metabolism. A negative nitrogen
balance indicates that the protein needs of the body are not being met.
Over time, this may lead to reduced gains in muscle mass and strength.
However, Dr Lemon also reported that at higher protein intakes (2.6
grams per kilogram of bodyweight, which works out at 214 grams for a
180 pound male) nitrogen balance appeared to plateau. In other words,
a protein intake of 2.6 grams per kilogram of bodyweight appears to represent
nutritional overload.
Based on these findings, Dr. Lemon suggests 1.6-1.7 grams of protein
per kilogram of bodyweight for individuals involved in strength training.
For endurance athletes, the figure is a little lower - around 1.3 grams
per kilogram of bodyweight.
For a 180-pound male, this gives a suggested protein intake of between
131 grams and 139 grams per day. This is not too different from the Zone
diet recommendation of 127-158 grams per day.
The Zone diet has come in for a good deal of criticism from
nutritionists and exercise scientists. However, it's essentially a restricted
calorie diet. For anyone who wants to lose body fat, there's no reason
why the Zone diet would not prove effective.
About the Author
 Christian Finn holds a master's degree in exercise science, is a certified personal trainer and has been featured on BBC TV and radio, as well as in Men's Health, Men's Fitness, Muscle & Fitness, Fit Pro, Zest and other popular fitness magazines.
If you want better, faster results from the time you spend in the gym, click here now for instant access to his step-by-step muscle-building and fat-burning workout routines.
Related Articles
1. Akermark, C., Jacobs, I., Rasmusson, M., & Karlsson,
J. (1996). Diet and muscle glycogen concentration in relation to physical
performance in Swedish elite ice hockey players. International
Journal of Sport Nutrition, 6, 272-284
2. Cheuvront, S.N. (1999). The zone diet and athletic performance. Sports
Medicine, 27, 213-228
3. Lemon, P.R., Tarnopolsky, M.A., MacDougall, J.D., & Atkinson, S.A. (1992).
Protein requirements and muscle mass/strength changes during intensive training
in novice bodybuilders. Journal
of Applied Physiology, 73, 767-775
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