Since the 1930s there has been a body of research telling us that if we would restrict our calories to less than we need, we could live longer lives. I used to be the director of a weight loss program for morbidly obese patients; one of the patients told me that you don’t really live longer; it just seems like it.

On August 29, 2012 in Nature, the results of a 25-year study of rhesus monkeys  gave some credence to my patient’s wry comment. If this study of monkeys does transfer to people, you do not live longer on average if you eat fewer calories.  The experimental group of monkeys was fed 30% less than the control group of monkeys. The study found that it does not appear that simple calorie count is a trigger for longevity. This result offers some relief to those of use who enjoy the pleasures of moderate portions of delicious food. Instead of reduced calories, the study found that genetics and the composition of the diet matter more to longevity than calorie restriction. Whew!!! However, the results are complicated, and the science in this area is not too definitive in any direction.

I’ve always struggled with the low calorie research. Why? You ask. Because, for me, just maintaining normal weight is challenging. I enjoy the freedom to have a piece of pie sometimes and gelato another. If you were trying to consume 30% fewer calories and still get the nutrients that you need from good healthy foods, there wouldn’t be many calories left in your calorie budget for an occasional digression in the eating plan. And I, for one, believe that the food I eat is one of the joys and blessings of life. When you’re feeding monkeys, it’s a bit easier. The feeding trays are filled with ‘X’ amount of feed – the monkeys get what’s there. But when you live in a real world of humans, Aunt Martha makes her famous Peach Cobbler, and whoopsie; there goes your goal of 30% calorie restriction.

If you take a second look at the monkey study you will notice that those on the restricted diet had less cardiovascular disease, also less cancer and diabetes. What’s really weird is that that decrease in disease did not translate into longer life spans. It’s almost as if deficit eating makes the monkeys even worse off, in order to offset the advantage of less serious diseases that are strongly connected to shorter lives. If you take a third look at the monkey studies, you discover that they were receiving up to 28.5% of the diet as sucrose (table sugar). That doesn’t sound very healthy. Note: look at the link above and then scan down – you’ll discover that there is still quite a bit of mixed results in the various studies related to calorie restriction.

One thing that we do know is that calorie restriction causes a stress response; but science has, so far, not been able to sort out the benefits and/or problems of this hunger stress.

There is precious little evidence that calorie restriction slows ageing in humans. And if you look at study of humans (not monkeys, rats, mice, yeast, flies or worms) then consider Amy Berrington de Gonzalez’s study.  It was reported in The New England Journal of Medicine and found that people of average weight tend to live the longest. She and her group found that the group with a BMI (men or women) of 20.0 to 24.9 had the lowest mortality. Again Whew!!  Note that Barrington’s study found that either the low end or the high end of weight in humans is associated with shorter life span. Maybe that applies to the monkeys too, and some combination of being on the low end of the monkey weight continuum, AND the extra sucrose overcame the benefits of lower heart disease, cancer, and diabetes.

There does seem to be a consensus that human lifespan is not fixed; that we can influence our lifespan by eating a healthy diet, maintaining normal weight, getting adequate sleep and exercising our bodies. As a public health nutritionist, it seems to me that the researchers should keep working on the longevity/calorie restriction issue, but the FAR greater issue is for the general population to move out of the overweight/obesity weight range. There is no question that the epidemic proportion of overweight/obesity does reduce lifespan. Let’s work on that huge goal, before we strive to eat 30% fewer calories than needed to maintain normal weight.

We can maintain normal weight, with exercise and lots of attention to what we eat. And for those of you who enjoy a treat now and then, let’s let the researchers continue their work, while we bring a little pleasure to our lives with a low to moderate amount of treats.