Wednesday, February 29, 2012

The Paleo Diet

Proposition

The Paleo Diet supposedly mimics the diet of hunter-gatherers from the Paleolithic era (which ended about 10,000 years ago). Intuitively, it includes foods that can be hunted (meat, fish, etc...) or gathered (eggs, fruit, vegetables, etc...), but not those that can't (grains, legumes, sugar, etc...). In practice, this usually means eating a large amount of fat and protein, but not very many carbohydrates. In this sense, it is a subset of low-carb diets (but this is not true of all versions of the Paleo Diet). The proponents of the Paleo Diet explain its efficacy by resorting to evolutionary explanations, which some dietitians and anthropologists dispute. I will skip over the theoretical debate completely and only focus the truth value of the following proposition:  

The Paleo Diet will work (for me).

What does it mean for a diet to work? Time to operationalize. For the purposes of my self-experiment, I will consider a diet to work if and only if, while on it:

1. I lose a significant amount of fat. In this case, 10 lbs seems reasonable.

2. I maintain my strength and endurance. If I am unable to continue my weekly weightlifting regimen at my current weight levels, I will consider this condition not to be met. Also, if I am unable to continue to run the same distance in a given amount of time, then the diet will not count as working.

3. I don't otherwise become unhealthy. More precisely, this would require that I don't get any abnormal values on the biochemical analysis (blood test) included in a physical examination at my doctors office.

Prior Belief

There are several reasons for doubting whether any diet will work for me, let alone a high-fat diet:

1. I'm in a reference class in which 66% of the people develop obesity before reaching 60 years old. It already isn't looking good.

2. According to my back-of-the-envelope calculations, I will be eating much more than the Food and Drug Administration's daily reference values (DRV) for saturated fatty acids, cholesterol, and probably protein. Also, I will be eating more than 90% less than the DRV for carbohydrates. If you think the FDA has any idea what they are talking about, then this should be worrying.

3. Since I have the CC version of the rs1801282 single-nucleotide polymorphism (SNP), 23andme's health analysis software advises me that "a diet high in monounsaturated fat is not likely to have beneficial effects on BMI or waist circumference". Also, I have the AG version of the rs662799 SNP, so "dietary fat consumption is not associated with changes in BMI". In other words, I don't have any information about my genetics that would lead me to think that this is going to be a particularly effective diet.

Evidence

According to the data, I lost approximately 30 lbs since starting the Paleo Diet. This brings me from a not-so-great BMI of 26.5 to a much safer BMI of 21.5. The Singapore Government's Health Promotion Board claims that a BMI in the range of 23-27.4 poses a "moderate risk of developing heart disease, high blood pressure, stroke, diabetes", but that a BMI in the range of 18-22.9 constitutes a "low risk (healthy range)". This easily beats my requirement of losing 10 lbs in order to claim that the Paleo Diet works.

I continued my regular weight-lifting routine (more or less) through the entire time I was on the diet and have increased my weight on both the back squat and deadlift. My bench press stagnated, but didn't get any worse. Also, I am now running a greater distance in the same amount of time as I was before starting the diet. This means that 2 of my 4 fitness goals and predictions have already been confirmed on PredictionBook (squat and deadlift, but not bench press or running).

I did finally go in for my yearly (actually less) physical exam. I should note that I did not fast before my blood test (which the doctor didn't think warranted me losing sleep in order to do, but that the lab tech seemed to think was important). My cholesterol is somewhat high, but is still within the typical (healthy) range. Over the phone, my doctor advised me that my cholesterol was on the high end of the normal (healthy) range, but it appears my actual lab results (of which I just obtained a copy) are showing a "flag" on my total cholesterol. Here are my actual results:

  • Total cholesterol: 207 mg/dL
  • Triglycerides: 102 mg/dL
  • HDL cholesterol: 72 mg/dL
  • LDL cholesterol: 115 mg/dL

According to the American Heart Association (AHA), a total cholesterol between 200-239 mg/dL is considered "borderline high" and puts you at higher risk of coronary heart disease than for values less than 200 mg/dL, but much less so than for values over 240 mg/dL. The AHA thinks my LDL cholesterol is "near or above optimal", so there isn't much to worry about there. Also, my triglyceride level is "normal".

On the other hand, the AHA also says that more important than the total number is the ratio of total cholesterol to HDL cholesterol. They recommend keeping the ratio under 5:1 and striving for 3.5:1. My ratio comes out to 2.9:1, which is even lower than what you are supposed to strive for! I'm not exactly sure how to interpret this result. This does put some doubt as to whether the diet has successfully met my initial success conditions, but it certainly isn't an outright falsification. Of course, advocates of the Paleo Diet usually claim that the common understanding of cholesterol by medical practitioners is simply wrong. I don't have the relevant background knowledge to evaluate their arguments for myself, so I assume that mainstream medicine is correct and will count this as a minor point against the efficacy of the diet.

Blood tests aren't the only indicator of potential heart problems. Blood pressure is another. I tracked my blood pressure and pulse over the last six days and the result is less ambiguous than the blood test. The AHA recommends a systolic blood pressure of less than 120 mmHg and a diastolic blood pressure of less than 80 mmHg.



My blood pressure readings were consistently within the healthy ranges set by the AHA.

Posterior Belief

The experiment provides some confirmation of the proposition, but is somewhat ambiguous due to not completely fulfilling the third condition. I plan on continuing with a (slightly modified) version of my current diet pending further testing.

Part 2 | Part 3 | Part 4

5 comments:

  1. what does the data look like *before* you started the paleo diet? It's impossible to evaluate whether the paleo diet caused your weight loss or you were already on a downward trend without this information.

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    Replies
    1. Matt, even if I *was* tracking all those metrics before I started, my reasoning could still be falling prey to the post hoc ergo propter hoc fallacy. You are correct though; the quality of the evidence would be much better if I had been collecting the same data ahead of time. Unfortunately, it only dawned on me that I should obtain objective measures of the results shortly after I decided I should to change my diet. On the other hand, observing my Facebook pictures from the 6 months previous to starting the experiment seems to indicate a roughly stable (much higher) weight (although, this is somewhat vague and subjective). Since this is really my first attempt at serious self-tracking, I anticipate that the evidence collected from my next experiment will be of much higher quality than this one. Thanks for the feedback.

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    2. Yeah, inferring causality is hard. You're right about my language, it was too strong even for what I was trying to say. I figured you had some less objective way looking at your weight pre-diet. That is a pretty steep drop, after all, that I'm sure you would have noticed had it started earlier.

      I'd be interested in hearing any other noticeable effects the paleo diet had on you. I've been experimenting with it myself.

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    3. Matt, I have experienced a lot less of what I call "mind-fog". Also, I seem to require less sleep for a given level of alertness. Besides that, my back and foot pain has diminished slightly (but these were already declining, so it might not have anything to do with the diet). The only negative subjective experience I can think of is stomach pain, but I'm not sure how often I had stomach pain before. I have only had it 2-3 times in the last 2 months, which I don't consider to be a very significant downside.

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