Have you heard about the "obesity paradox"? The idea is that in certain circumstances, it is healthier to be fat. What's the science in support of this idea? Should we get fat to stay healthy?
One study, which provides some insight into this "obesity paradox," came from Sweden's extensive registry of patients with blockages in the arteries of their hearts. More than 50,000 such heart patients were studied. Each had significant blockages in the arteries of the heart, a condition that leads to heart attacks and sudden cardiac deaths. When looking at the most important outcome, death from any cause, morbidly obese and underweight patients had the worst outcomes, as might be expected. The surprising result was that overweight and obese heart patients had better outcomes than heart patients of normal weight.
One note of caution before you decide to gain weight for better health: All of these patients had heart disease. What we can conclude from the study is this: In a sample of Swedes with coronary heart disease (blockages in the heart's arteries), those who were overweight and obese lived longer than those of normal weight.
What's a doctor to do when confronted with a patient with heart disease who is overweight? Should the doctor avoid recommending weight loss, fearing that the patient's outcome will worsen? Are heart patients who are of normal weight a different population from heart patients who are fat?
Perhaps our cousins, the baboons, can help us understand. For several decades, Dr. Robert Sapolsky has studied the olive baboons in the Masai Mara National Reserve in the Serengeti Plain of Kenya. I don't think anyone will ever attempt to repeat Dr. Sapolsky's research.
Imagine darting a male baboon with a blowgun in order to induce anesthesia, and then putting him in a sack, carrying him to your tent, drawing blood samples, infusing epinephrine intravenously, taking heart rate and blood pressure, and then bringing him back to the forest before he awakens from the drug. Have you ever seen the canines on a fully-grown male baboon?
A natural experiment occurred in one of the troops that Dr. Sapolsky had been following. A tourist resort began dumping its food waste in a large pit right in the middle of the baboons' territory. The normally sleek and fit baboons began gaining weight. In addition, their "bad" cholesterol went up, and so did their insulin levels. They were now prone to obesity, diabetes and heart attacks.
The baboons expended fewer calories, but consumed the same number of calories as before. Something had gone awry in their metabolic system when they began eating the human food remains.
What exactly were the baboons eating? Dr. Sapolsky sifted through the garbage and found:
... fried drumsticks or a slab of beef left over by a tourist with eyes bigger than his stomach; fruit salad gone a bit bad, perhaps left too long on the sun-drenched buffet table; fragments of pies and cakes, and alarming yellow dollops of custard pudding, nibbled at by a disciplined dieter -- processed sugars, fat, red meat and cholesterol, our modern Four Horsemen of the Apocalypse.
It turns out that the story is even a bit more nuanced. The "garbage dump baboons" fell into two distinct categories. One group got fat and developed the metabolic changes of pre-diabetes, but had only moderately elevated "bad" cholesterol levels. The second group had only modest weight gain and did not develop pre-diabetes, but had extremely high levels of "bad" cholesterol.
In other words, two distinct patterns emerged in response to the "garbage dump" diet. In some of the baboons the result was marked by weight gain and pre-diabetes. The other group appeared resistant to pre-diabetes and weight gain, but had marked increases in the type of cholesterol predictive of heart attacks.
If baboons can respond to human food with several different metabolic patterns, it seems likely that humans do as well. Could this help explain the "obesity paradox"? Perhaps the normal weight heart patients are metabolically similar to the "garbage dump baboons" who were resistant to gaining weight and pre-diabetes, but were prone to heart attacks.
The overweight and obese heart patients with better outcomes might be similar metabolically to the pre-diabetic, overweight "garbage dump baboons," who were more resistant to cholesterol elevations which predict heart attacks. You would expect this group to have less severe heart disease than the other.
Several different pathological pathways emerging from a single insult is just what happens with tobacco. One in eight heavy tobacco smokers may get lung cancer. Some smokers, who are resistant to lung cancer, will get emphysema, and others get neither cancer nor emphysema, but blockages in the arteries of their legs.
The "garbage dump" diet reliably produced pathology in baboons, with two distinct metabolic patterns. What in the diet was the culprit? I'm betting that it was the sugar from the fruit salad, pies, cakes and custard. That would be most compatible with what we know about sugar's toxicity in humans. It's also in keeping with the human research outcomes, which have linked sugar to multiple pathological pathways leading to diabetes, heart attacks, strokes, hypertension, cancer, obesity, fatty liver disease and death from heart disease.
Does our present high-sugar diet do to us what the "garbage dump diet" did to the baboons? Weight gain, pre-diabetes and alarming cholesterol elevations are all results of our diet too. Like the baboons, we humans will certainly respond to dietary insults in a variety of ways. Some of us are more prone to weight gain and diabetes and others more prone to heart disease.
Perhaps the obesity paradox is not a paradox at all, but the expected variation in metabolic responses to our unhealthy diet. All of the "garbage dump baboons" had unhealthy metabolic profiles whether they were prone to weight gain or not. Are we seeing the same unhealthy outcomes in "junk food humans"?
A sad postscript to the story is that half the "garbage dump" troop was killed by bovine tuberculosis from eating contaminated meat from the dump. It was the first time the disease was reported in wild primates.