“The unexamined life is not worth living.” – Socrates
For the past two years, I have followed a rough interpretation of Barry Sears’ Zone Diet [1], which has allowed me to see improvements in my training for endurance races, feel mentally sharp and energized, and maintain a healthy weight and body composition. But is this diet actually the optimal one for me? I decided to find out.
Introduction
The Zone Diet aims to limit systemic inflammation and its myriad related problems by balancing the three macronutrients—carbohydrates, protein and fat—at each meal. It measures these nutrients in a Sears-invented unit called “blocks,” where one block of carbohydrates equals 9 grams (g) carbohydrate, one block of protein equals 7 g protein and one block of fat equals 1.5 g fat. Sears claims that the amount of food a person needs over the course of a day is based on his protein requirement, which in turn is based on lean body weight and activity level. For example, a very active 170-pound man with 10% body fat would require approximately 140 g or 20 blocks of protein each day [2]. Based on his protein requirement, he would also require 20 carbohydrate blocks and 20 fat blocks. Because the Zone Diet encourages adherents to balance their macronutrient blocks at each meal, a “two block meal” would consist of two blocks each of protein, carbohydrates and fat, such as two ounces (oz) chicken (weighed when raw) and three cups of green beans cooked in 2/3 teaspoon of olive oil. For the most part, the Zone Diet categorizes foods by the predominant macronutrient (e.g. 1/4 cup of black beans is considered one carbohydrate block, even though black beans also contain a fair amount of protein).
After a period of trial and error, I found that 20 blocks of carbohydrates and protein and 40 blocks of fat (where the number of fat blocks at each meal is double the number of protein and carbohydrate blocks) seemed to work well in matching my daily energy expenditure, and the experiment described in this article uses that distribution as a baseline. In this experiment, I wanted to see whether varying the ratio of carbohydrate to protein had any effect on my overall health and well-being. I divided the trial into three four-week periods as follows:
- Weeks 1 through 4: increase carbohydrate intake by one block at each meal and decrease protein intake by one block at each meal (so a “two block meal” under my previous diet would now consist of three blocks (27 g) of carbohydrates, one block (7 g) of protein and four blocks (6 g) of fat).
- Weeks 5 through 8: increase protein intake by one block at each meal and decrease carbohydrate intake by one block at each meal (making a “two block meal” consist of one block (9 g) of carbohydrates, three blocks (21 g) of protein and four blocks (6 g) of fat).
- Weeks 9 through 12: return to my previous diet of equal carbohydrate and protein blocks and double fat blocks.
This procedure allowed me to make small changes to my food intake and provided a range of carbohydrate to protein ratios for comparison. As an illustration, here are sample days for each experimental condition:
To determine the effect of each diet on my overall health and performance, I collected the following data:
- Heart rate – measured each day when I woke up and before I went to bed and 30, 60 and 90 minutes after each meal using the FoodDetective app by Better Baby LLC [3]
- Central nervous system (CNS) function – measured 30 minutes after each meal with a tap test and reaction time test using the Performance app by Smudge.io [4]
- Brain function – measured 30 minutes after each meal with the Matching Pairs game on the Fit Brains app by Rosetta Stone [5]
- Workout performance – measured by recording each workout and grading each workout that had a predefined goal (such as a previous personal best or an expected level of performance) as a success or failure
- Sleep – measured each night by recording the number of instances of light sleep or waking using the SleepBot app by SleepBot LLC [6]
- Body composition – measured each week by recording my weight and body fat using circumference measurements and formulas defined by the National Academy of Sports Medicine (NASM) and Dr. Barry Sears
Here are the results [7]:
1. Heart rate
There were no significant variations in my heart rate 30, 60 or 90 minutes after eating based on the carbohydrate to protein ratio of my previous meal, and no significant variations in mean heart rates for any of the diets as a whole.
2. CNS function
The average tap test score for my right hand was 66 for the high carbohydrate diet, 68 for the high protein diet and 71 for the balanced diet. The average tap test score for my left hand was 60 for the high carbohydrate diet, 61 for the high protein diet and 60 for the balanced diet. My average reaction time was 270 milliseconds (ms) for the high carbohydrate diet, 240 ms for the high protein diet and 232 ms for the balanced diet.
3. Brain function
My average brain game score was 3616 for the high carbohydrate diet, 3867 for the high protein diet and 4005 for the balanced diet. Because I moved from the high carbohydrate diet to the high protein diet to the balanced diet over the course of the twelve weeks, I realized that the improvements in the metrics for CNS and brain function could have resulted from accumulated practice over the twelve weeks and may have been unrelated to changes in my diet. To test this possibility, I recently completed a single week each of the balanced diet, the high protein diet and the carbohydrate diet (in that order), and measured CNS and brain function as before.
Over the course of these final three weeks, my average right-hand tap test score was 74 for the balanced diet, 71 for the high protein diet and 70 for the high carbohydrate diet. My average left-hand tap test score was 60 for the balanced diet, 59 for the high protein diet and 59 for the high carbohydrate diet. My average reaction time was 223 ms for the balanced diet, 227 ms for the high protein diet and 232 ms for the high carbohydrate diet. My average brain game score was 4007 for the balanced diet, 4013 for the high protein diet and 3941 for the high carbohydrate diet. Since these metrics did not improve (and generally worsened) as I changed diets over these latter three weeks, I believe the changes in CNS and brain function observed in the first twelve weeks were due (at least in part) to changes in my diet.
Looking at individual meals, my best performances on CNS and brain function tests followed meals with a ratio between 2 blocks carbohydrates to 3 blocks protein (6 g carbohydrates to 7 g protein) and 1 block carbohydrates to 1 block protein (9 g carbohydrates to 7 g protein).
4. Workout performance
I was successful in 17 of 25 workouts (68.0%) on the high carbohydrate diet, 15 of 20 workouts (75.0%) on the high protein diet and 20 of 30 workouts (66.7%) on the balanced diet.
5. Sleep
There were no significant variations in my sleep patterns between the three different diets.
6. Body Composition
Photographs taken before Week 1 and after Weeks 4, 8 and 12 confirmed that I was least lean on the high carbohydrate diet, lost body fat on the high protein diet, and leveled off on the balanced diet.
Conclusions
In general, two observations stood out to me from this experiment. First off, no individual meal, regardless of carbohydrate to protein ratio or overall nutritional value, resulted in major or irreversible variations in any of the metrics tested. If I ate poorly at a given meal, I might see a slight increase in heart rate or marginally reduced tap test score. Yet if my next meal was healthier, the metrics rebounded toward the mean of my current diet. However, I was surprised at the significant changes in my physical and mental performance over the course of a week or month as a result of these relatively small adjustments in my diet. Throughout these twelve weeks, every meal I ate contained at least one source of carbohydrate, protein or fat. Oftentimes, I ate the exact same foods, just in different proportions depending on the parameters of my current diet. Yet adjusting the ratio of carbohydrate to protein in a consistent manner for an extended period of time produced significant variations in the means of several performance metrics. In particular, eating a balanced diet or one slightly higher in protein improved my CNS and brain function, my physical performance and my body composition in comparison to a diet slightly higher in carbohydrates.
Because the balanced diet resulted in the highest scores for central nervous system and brain function and the high protein diet produced the greatest improvements in body composition and physical performance, I plan to incorporate both of these diets moving forward. Given that my best brain and CNS performance followed meals with a ratio between 6 to 9 g carbohydrates to 7 g protein, I will attempt to maintain this ratio in my meals going forward. Without necessarily recording detailed measurements as in this experiment, I will continue to monitor my health and performance subjectively and will corroborate these observations with regular blood tests.
In a big picture sense, this article is not intended to encourage you to follow any particular diet, or even to undergo this level of self-experimentation on your own diet. The idea is simply to provide one small example of how to think about making changes in your own life. We all have aspects of our lives we want to improve, whether they are related to health, education, business or relationships. In order to make meaningful change, we need to explicitly define and measure that meaning. If you don’t know exactly what your target is, you will never know when you’ve hit it, and you will waste time and energy on half-measures that don’t get you closer to your goal. It is only human to strive for change and improvement, but we must examine our efforts in order to reach our life’s aims.
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1. For a complete overview of and justification for the Zone Diet, see Sears, Barry. Enter the Zone: A Dietary Road Map. New York: Harper Collins, 1995.
2. The calculation is [1 – [body fat percentage]] x [weight in pounds] x [activity level factor], e.g. (1-0.1) x 170 x 0.9 = 137.7 g protein, rounded up to 140 g protein for convenience in calculating blocks.
3. FoodDetective (2015). Better Baby LLC (Version 1.0.3). Mobile application software. Retrieved from http://itunes.apple.com.
4. Performance (2015). Smudge.io (Version 1.1.1). Mobile application software. Retrieved from http://itunes.apple.com.
5. Fit Brains (2015). Rosetta Stone (Version 3.5). Mobile application software. Retrieved from http://itunes.apple.com.
6. SleepBot (2015). SleepBot LLC (Version 1.2.0). Retrieved from http://itunes.apple.com.
7. You can download all the data from this experiment here: The Socratic Diet Data