Diabetic Mediterranean Diet

Gary Taubes’s new book, Why We Get Fat: And What To Do About It, comes on the market later this month.  I give it five stars per Amazon.com’s ranking system (I love it).

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At the start of my medical career over two decades ago, many of my overweight patients were convinced they had a hormone problem causing it.  I carefully explained that’s rarely the case.  As it turns out, I may have been wrong.  And the hormone is insulin.

Mr. Taubes wrote this long-awaited book for two reasons: 1) to make the ideas in his 2007 masterpiece (Good Calories, Bad Calories) more accessible to the public, and 2) to speed up the process of changing conventional wisdom on overweight.  GCBC was the equivalent of a college-level course on nutrition, genetics, history, politics, science, physiology, and biochemistry. Many nutrition science geeks loved it while recognizing it was too difficult for the average person to digest.

Paradigm Shift

The author hopes to convince us that “We don’t get fat because we overeat; we overeat because we’re getting fat.”  We need to think of obesity as a disorder of excess fat accumulation, then ask why the fat tissue isn’t regulated properly.  A limited number of hormones and enzymes regulate fat storage; what’s the problem with them?

Mr. Taubes makes a great effort convince you the old “energy balance equation” doesn’t apply to fat storage.  You remember the equation: eat too many calories and you get fat, or fail to burn up enough calories with metabolism and exercise, and you get fat.  To lose fat, eat less and exercise more.  He prefers to call it the “calories-in/calories-out” theory.  He admits it has at least a little validity.  Problem is, the theory seems to have an awfully high failure rate when applied to weight management over the long run.  We’ve operated under that theory for the last half century, but keep getting fatter and fatter.  So the theory must be wrong on the face of it, right?  Is there a better one?

So, Why DO We Get Fat?

Here is Taubes’s explanation.  The hormone in charge of fat strorage is insulin; it works to make us fatter, building fat tissue.  If you’ve got too much fat, you must have too much insulin action.  And what drives insulin secretion from your pancreas?  Dietary carbohydrates, especially refined carbs such as sugars, flour, cereal grains, starchy vegetables (e.g., corn, beans, rice, potatoes), liquid carbs.  These are the “fattening carbs.”  Dozens of enzymes and hormones are at play either depositing fat into tissue, or mobilizing the fat to be used as energy.  It’s an active process going on continously.  Any regulatory derangement that favors fat accumulation will CAUSE gluttony (overeating) or sloth (inactivity).  So it’s not your fault. 

What To Do About It

Cut back on carb consumption to lower your fat-producing insulin levels, and you turn fat accumulation into fat mobilization.

Before you write off Taubes as a fly-by-night crackpot, be aware that he’s received three Science-in-Society Journalism Awards from the National Association of Science Writers.  He’s a respected, professional science writer.  Having read two of his books, it’s clear to me he’s very intelligent.  If he’s got a hidden agenda, it’s well hidden.

One example  illustrates how hormones control growth of tissues, including fat tissue.  Consider the transformation of a skinny 11-year-old girl into a voluptuous woman of 18. Various hormones make her grow and accumulate fat in the places we now see curves.  The hormones make her eat more, and they control the final product.  The girl has no choice.  Same with our adult fat tissue, but with different hormones. If some derangement is making us grow fatter, it’s going to make us more sedentary (so more energy can be diverted to fat tissue) or make us overeat, or both.  We can’t fight it.  At not least very well, as you can readily appreciate if look at the people around you at any American shopping mall.

This’N’That

Taubes’s writing is clear and persuasive.  He doesn’t beat you over the head with his conclusions. He lays out a logical series of facts and potential connections and explanations, helping you eventually see things his way.  If insulin controls fat storage by building and maintaining fat tissue, and if carboydrates drive insulin secretion, then the way to reduce overweight and obesity is carbohydrate-restricted eating, especially avoiding the fattening carbohydrates.  I’m sure that’s true for many folks, perhaps even a majority.

If you’re overweight and skeptical about this approach, you could try out a very-low-carb diet for a couple weeks or a month at little expense and risk (but not zero risk).  If Mr. Taubes and I are right, there’s a good chance you’ll lose weight.  At the back of the book is a university-affiliated low-carb eating plan.

If cutting carb consumption is so critical for long-term weight control, why is it that so many different diets—with no focus on carb restriction—seem to work, if only for the short run?  Taubes suggests it’s because nearly all diets reduce carb consumption to some degree, including the fattening carbs.  If you reduce your total daily calories by 500, for example, many of those calories will be from carbs.  Simply deciding to “eat healthy” works for some people: stopping soda pop, candy bars, cookies, desserts, beer, etc.  That cuts a lot of fattening carbs right there.

Losing excess weight or controlling weight by avoiding carbohydrates was the conventional wisdom prior to 1960, as documented by Mr. Taubes.  Low-carb diets for obesity date back almost 200 years.  The author attributes many of his ideas to German internist Gustav von Bergmann (1908).   

Taubes discusses the Paleolithic diet, mentioning that the average paleo diet derived about a third of total calories from carbohdyrates (compared to the standard American diet’s 55% of calories from carb).  My prior literature review  found 40-45% of paleo diet calories from carbohydrate.  I’m not sure who’s right.

Minor Bone of Contention RE: Coronary Heart Disease

Mr. Taubes provides numerous scientific references to back his assertions.  I checked out one in particular because it didn’t sound right.  Some background first. 

Reducing our total fat and saturated fat consumption over the last 40 years was supposed to lower our LDL cholesterol, thereby reducing the burden of coronary heart disease, which causes heart attacks.  Instead, we’ve experienced the obesity epidemic as those fats were replaced by carbohydrates.  Taubes mentions a 2009 medical journal article by Kuklina et al, in which Taubes says Kuklina points out the number of heart attacks has not decreased as we’ve made these diet changes.  Kuklina et al don’t say that.  In fact, age-standardized heart attack rates have decreased in the U.S. during the last decade. 

Furthermore, autopsy data document a reduced prevalence of anatomic coronary heart disease in people aged 20-59 from 1979 to 1994, but no change in prevalence for those over 60. The incidence of coronary heart disease decreased in the U.S. from 1971 to 1998 (the latest reliable data).  Death rates from heart disease and stroke have been decreasing steadily over the last 40 years in the U.S.; coronary heart disease death rates are down by 50%.  I do agree with Taubes that we shouldn’t credit those improvements to reduced total and saturated fat consumption.  [Reduced trans fat consumption may play a role, but that’s off-topic.] 

I think Mr. Taubes would like to believe that coronary artery disease is either more severe or unchanged in the last few decades because of low-fat, high-carb eating.  That would fit nicely with some of his theories, but it’s not the case.  Coronary artery disease is better now thanks to a variety of factors, but probably not diet (setting aside the trans-fat issue).

Going Forward

Low-carb dieting was vilified over the last half century partly out of concern that the accompanying high fat consumption would cause premature heart attacks, strokes, and death.  We know now that total dietary fat and saturated fat have little to do with coronary heart disease and atherosclerosis (hardening of the arteries), which sets the stage for a resurgence of low-carb eating.  

I advocate Mediterranean-style eating as the healthiest, in general.  It’s linked with prolonged life and lower risk of heart disease, stroke, dementia, diabetes, and cancer.  On the other hand, obesity is a strong risk factor for premature death and development of heart disease, stroke, diabetes, and cancer.  If consistent low-carb eating cures the obesity, is it healthier than the Mediterranean diet?  Maybe so.  Would a combination of low-carb and Mediterranean be better?  Maybe so.  I’m certain Mr. Taubes would welcome a decades-long interventional study comparing low-carb with the Mediterranean diet.  But that’s probably not going to happen in our lifetimes. 

Gary Taubes rejects the calories-in/calories-out theory of overweight that hasn’t done a very good job for us over the last 40 years.  Taubes’s alternative ideas deserve serious consideration.

Steve Parker, M.D.

Update December 18, 2010: I found Mr. Taubes’s reference for stating that Paleolithic diets provide about a third of calories from carbohydrate (22-40%), based on modern hunter-gatherer societies).  See References below.   

References:
Coronary heart disease autopsy data:  American Journal of Medicine, 110 (2001): 267-273.
Reduced heart attacks:  Circulation, 12 (2010): 1,322-1,328.
Reduced incidence of coronary heart disease:  www.UpToDate.com, topic: “Epidemiology of Coronary Heart Disease,” accessed December 11, 2010.
Death rates for coronary heart disease:  Journal of the American Medical Association, 294 (2005): 1,255-1,259.

Cordain, L., et al.  Plant-animal subsistance ratios and macronutrient energy estimations in worldwide hunter-gatherer diets.  American Journal of Clinical Nutrition, 71 (2000): 682-692.

Disclosure:  I don’t know Gary Taubes.  I requested from the publisher and received a free advance review copy of the book.  Otherwise I received nothing of value for this review.

Disclaimer:   All matters regarding your health require supervision by a personal physician or other appropriate health professional familiar with your current health status.  Always consult your personal physician before making any dietary or exercise changes.

Update April 22, 2013: 

As mentioned above, WWGF was based on Taubes’ 2007 book, Good Calories, Bad Calories. You may be interested in a highly critical review of GCBC by Seth at The Science of Nutrition.