The Zone diet was introduced in the mid 1990s, by Dr. Barry Sears, a biochemist, when he published his book Enter The Zone: A Dietary Roadmap. Today it is widely known, and it is generally a popular program. While I am not a “Zoner,” I did experiment with the diet for about six months in 2010, for no significant reason beyond curiosity.
In the following text I offer an overview of the Zone diet, a list of its oft cited pros and cons, and my subjective review of it based on my limited six-month “Zone” foray.
Overview of the Zone Diet
Dr. Sears claims that the Zone diet regulates hormone levels, resulting in weight loss and disease prevention. He focuses mostly on insulin, a hormone secreted by the pancreas that tempers spikes in blood sugar levels. Insulin does its work by forcing cells to uptake glucose (sugar) from blood so it can be stored as glycogen (a future source of energy) in the muscles and liver. The amount of glycogen the muscles and liver can store is, however, finite; once they reach their storage limits, additional blood sugar is ultimately turned into body fat. Insulin’s antipode is glucagon, also a hormone produced by the pancreas. Glucagon forces the liver to convert glycogen back into glucose where it can serve as an energy source. In a nutshell, insulin takes sugar out of the blood when it is too plentiful, glucagon puts it back in when it is lacking.
Constantly eating too much—particularly insulinogenic foods—is largely considered unhealthy. Sears maintains that following the Zone diet helps us reduce our insulin levels, and increase our glucagon levels. He asserts that increasing our glucagon levels helps our bodies metabolize our fat stores to lose weight, and that modulating our insulin levels reduces our risks of disease.
In athletics, being in “the zone” is usually associated with “operating at a maximal performance level.” In the case of Dr. Sears’ diet, it is essentially associated with a state of “homeostasis,” a point where the body is in optimal health. To achieve “the zone,” Sears believes we need to eat a 40/30/30 ratio of carbohydrates, proteins, and fats. He maintains that a “zone meal” will keep us in “the zone” for about five hours, and that a “zone snack” will keep us in “the zone” for about two, to two-and-one-half hours. He has us calculate our daily protein needs using a formula based on a number of variables. From there he instructs us to eat a certain number of “zone blocks” each day based on our protein needs. Each “zone block” is comprised of seven grams of protein, nine grams of carbohydrate, and one and one-half grams of fat—a 40/30/30 macronutrient ratio. The basics of his plan are as follows:
- Eat five times per day (three meals and two snacks, all at a 40/30/30 ratio) whether hungry or not.
- Do not let more than five hours pass between daytime meals.
- Eat low-fat proteins; favor fresh fruits and vegetables as carbohydrate sources; add a bit of monounsaturated fat to every meal and snack.
- Meals should not exceed 500 calories; snacks should generally be around 100 calories.
- Eat grain-based carbs (breads, pastas) in moderation—treat them as condiments.
- Drink plenty of water, at least the proverbial eight glasses per day.
- Exercise Moderately.
Frequently Cited Pros and Cons of the Zone Diet
Twenty minutes of Google searching shows that there are many strong opinions of the Zone diet. Following are a few of the commonly cited pros and cons:
- The Zone diet includes many healthy food categories—fruits, low-starch vegetables, lean meats, monounsaturated fats, etc.
- Save for the avoidance of processed foods, the Zone diet is not overly restrictive.
- Eating five small meals per day quells hunger spikes.
- Anecdotal evidence shows that the Zone diet has successfully helped many people lose weight; and, while there has not been an abundance of scientifically valid studies performed, there have been a few randomized trials which show positive outcomes. For example, a study which can be found here on the Journal of the American Medical Association website shows that participants who followed the Zone diet in a controlled setting for a one-year time period lost weight and improved multiple health metrics.
- The Zone diet is high protein and fairly low carbohydrate, which can be taxing to the kidneys.
- Following a 40/30/30 macronutrient ratio at every meal can be difficult and time-consuming.
- The Zone diet has many skeptics among well-educated dieticians. In example, Samuel N. Chevront, PhD, RD, from the United States Army Research Institute of Environmental Medicine stated the following in an article entitled “The Zone Diet Phenomenon: A Closer Look at the Science behind the Claims” on the Journal of the American College of Nutrition website in reference to Sears’ book:
“… a review of the literature suggests that there are scientific contradictions in the Zone Diet hypothesis that cast questionable doubt on its potential efficacy.”
- Sears is criticized for being too ambiguous at times. His statement, “… maintain ‘a zone’ of insulin: not to high, not too low…,” is rather abstruse for example.
My Subjective Review of the Zone Diet
Having tried the Zone diet for only six months I cannot in good faith speak to its long-term efficacy. Furthermore, I was in good physical condition when experimenting with it; my baselines were not as such that dramatic improvements were likely. These facts aside, how did the program work for me? What do I think of the Zone diet?
I will start with what I liked. Echoing the pros listed above, I really enjoyed the foods I was able to eat while on the program. I felt little dietary restriction in terms of food choice.
As for my dislikes, trying to eat constantly at a 40/30/30 ratio was painstaking. I also felt calorically restricted. My exercise and athletic training at the time demanded at least 1,000 more daily calories than what the Zone diet prescribed. This being the case, I eventually deviated from the program and stepped up my daily caloric intake to about 3,700 calories to fuel my training. When doing so I still tried to maintain a 40/30/30 macronutrient ratio, meaning I was eating 250 to 300 grams of protein per day—an exceedingly difficult task.
Ultimately the Zone diet is not for me. To be fair though, I am generally not a fan of non-medically mandated, highly structured diets. The Zone plan may be a viable option for many though. I would say for those who do not require a high calorie diet, and for those who possess the patience and mental acuity (I believe you need to at least be a low-midpoint registrant on the Kim Kardashian to Stephen Hawking intellectual horsepower scale) to continually maintain a 40/30/30 macronutrient ratio, that the Zone diet is not a bad option.