Do Exercise & Diet Reduce Heart Disease for Diabetics?

Dr. Sears' Blog: Why Doesn’t Exercise and Diet Reduce Heart Disease for Diabetics?

That’s a good question after the June 24 issue of the New England Journal of Medicine reported on the failure of long-term diet and exercise to reduce heart disease in diabetics1. It had been known from earlier and shorter studies that diet and exercise in diabetics appeared to generate a decreased risk of cardiovascular disease. This is important since heart disease remains the number-one killer of Americans, and people with diabetes are two to four times more likely to develop heart disease. Since diabetes is becoming epidemic, this would suggest that heart disease should soon begin to escalate. But for exercise and diet have any benefits in any condition, they have to been continued forever. That is the motivation for this 13-year study that started with the best of intentions. However, last year the study was terminated at 10 years since it was clear that there were no cardiovascular benefits. Now that the study details have been published, it is clear why it failed.

First, all of the success of diet and exercise started to evaporate after the first year. Remember, the people who enter these studies are highly motivated with a terrible future awaiting them. So why would they seemingly throw away all the initial benefits of weight loss and reduction of blood sugar? Part of the reason can be explained by why most diet program fail: Willpower can only take you so far if your hormones are working against you. The end result is you are constantly hungry and always tired.

The amount of calories the subjects of this study consumed was low (between 1,200 and 1,800 calories per day), but the diet was a high-carbohydrate diet (that induces low blood sugar due to hyperinsulinemia). The diet was coupled with lots of exercise (that also lowers blood sugar). This is an almost surefire prescription to be constantly hungry and tired. As a result, compliance wanes.

On the other hand, if you are never hungry, then compliance is better. That was the case with another 13-year study of diabetic patients who had gastric bypass surgery. For these patients, there was a significant reduction in cardiovascular events2. The reason is probably hormonal. If you lose weight by diet and exercise, your levels of the hunger hormone ghrelin increases with no change in the levels of your satiety hormone, PYY. Just the opposite happens with gastric bypass surgery. Ghrelin doesn’t change, but PYY increases3. The result is that you are not hungry, and therefor your lifestyle compliance improves.

Of course, giving every diabetic gastric bypass surgery makes little sense. Giving them new, more powerful diabetic drugs with equally powerful side effects (like heart attacks) also makes no sense.

There may be third way: Functional foods that can increase PYY levels. But these have to be tasty (like pasta and rice) and convenient (only 90 seconds to make) since you have to take them the rest of your life. That’s the project I have been working on for the past six years. These new Zone PastaRX meals may be the answer, as they appear to reduce hunger without causing fatigue while eating the foods you like to eat.


  1. Wing RR et al. “Cardiovascular effects of intensive lifestyle intervention in type 2 diabetes.” NEJM DOI:10.1056/NEJMoa 1212914 (2013).
  2. Romeo S et al. “Cardiovascular events after bariatric surgery in obese subjects with type 2 diabetes.” Diabetes Care 35: 3613-2617 (2012).
  3. Olivan B et al. “Effect of weight loss by diet or gastric bypass surgery on peptide YY3-36 (PYY) levels.” Ann Surg 249: 948-953 (2009).

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About Dr. Barry Sears

Dr. Barry Sears is a leading authority on the impact of the diet on hormonal response, genetic expression, and inflammation. A former research scientist at the Boston University School of Medicine and the Massachusetts Institute of Technology, Dr. Sears has dedicated his research efforts over the past 45 years to the study of lipids. He has published 40 scientific articles and holds 14 U.S. patents in the areas of intravenous drug delivery systems and hormonal regulation for the treatment of cardiovascular disease. He has also written 14 books, including the New York Times #1 best-seller, The Zone, which have sold more than 6 million copies in the U.S. and have been translated into 22 different languages.


  1. Bruce Hicks

    I am a adult onset type 1 diabetic, insulin user since 1992. My doctor started me on prescription Omega 3 oils, 4 capsules daily ( approximately the maintenance dose recommended as a start in your program) many years ago and they have helped lower my Triglycerides among other benefits. I have always maintained an A1C of 5.2 to 6.0% but in recent years have become concerned about the amount of insulin I take to accomplish this. I assume injected insulin has pretty much the same affect and results that normally produced insulin has on the health – too much is not a good thing. I frequently read books on nutrition, supplementation and diet and that is how I came across your Omega 3 zone books. Based on what I have learned from those so far I have doubled the Omega 3 capsules to 8 (pharmacy grade) and started taking sesame oil (teaspoon/day) and have greatly cut back on the simple carbs in an effort to adopt the zone diet and life style. One thing that I have noticed is that I am running higher blood glucose sugars that require even more insulin to control. I don’t know of any illness or stress to account for this and wonder if that might be my liver pumping out some stored glucose to make up for what I am not getting in my diet. I’m getting plenty of protein and fats so that I am not feeling hungry often. Soon I will see my diabetic doctor for a routine checkup but wonder if you’ve seen this happen with other type 1’s on the omega 3 program?

    • Barry Sears

      I believe it may be the sesame oil that could be generating the problem. Although sesame oil contains certain phytochemicals that can inhibit delta-5-desaturase, it is also rich in omega-6 fatty acids. The insulin your are injecting to manage your diabetes will accelerate the formation of AA from those omega-6 fatty acids. What I might suggest is taking the Cellular Inflammation Test to determine your AA/EPA ratio and absolute levels of both AA and EPA. If that ratio or individual numbers are out of range, then that would indicate that my hypothesis may be correct and replacing with sesame oil with extra virgin olive would be the recommended dietary change.

  2. Thea Pretorius

    This blog had answers to many of the unanswered questions I have as a nutritionist. Thanks dr. Sears for working on all the puzzle pieces of the puzzle you have already. I have just qualified as a nutritionist and find it very difficult to tweezers out the real facts if everyone who discovers one puzzle piece makes it to fit the whole picture. I also hold a PhD in physiology and I think one of the challenges of today is to explain this complex work of art so that everyone gets the essentials to help them live their best lives ever. My favorite new piece of knowledge is the fact that both leptin and insulin cross the BBB to act as satiety hormones when inflammation is at the normal range. I have a blog with my nutritionist daughter and our goal is to explain these facts in a quest to promote natural heath through food. Your blog will definitely help us in our quest. Thanks again!

    • Dr. Sears

      I am glad my blog was of use. Nutrition is very complicated and as a result many try to simplify so much that it loses much of its scientific elegance.


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