Dieting today
Doctors are often asked by their patients: which diet is good for me? The answer is that it depends on whether you would like to lose weight, live longer or be healthy. Apparently, these goals are no longer confluent. If you are confused, then I am too. The more I read about diet, the less qualified I feel to give advice.
Let’s talk about weight loss first. What exactly do we mean by fat? By definition, any body mass index (or BMI) of more than 25 is considered overweight. To calculate your body mass index, divide your weight in kilogrammes by your height in metres squared, and there you have it. My own body mass index is 25.7, so I feel that I am in no position to set an example. Many studies use body mass index as a convenient proxy for body fat, but this is not always reliable. Few would call Arnold Schwarzenegger fat, though his body mass index is over 25. All would agree, though, that severe Class III obesity, which is a body mass index of more than 40, greatly increases the risk of many serious illnesses – but only one in 12 of all obese Americans fall into this extreme category. Believe me, Class III obesity is very fat. Some scientists, who are funded by the weight-loss industry, are advising people to strive for what they call a healthy body mass index, a goal that is often unattainable because of genetic differences. It is a perverse irony that we may be creating a disease of obesity simply by labelling it as such. Many diets are ineffective in the long term. With Class III obesity, it is relatively easy to shed weight initially, but as one gets closer to the ideal body mass index, weight loss grinds to a halt.
USA state funding for obesity research last year reached $400 million. Seventy-one million Americans spent about $46 billion on weight-loss products and services. Media reports on obesity doubled between 2003 and this year. Surgical procedures designed to counteract obesity trebled between 2000 and last year. The war on fat is making some people rich.
Now, let’s talk about longevity. As recently as 2003, the American Centre for Disease Control and Prevention likened the obesity epidemic to the plague of the Middle Ages, or the influenza pandemic of 1918-19, which killed more than 40 million. It warned that 400,000 Americans die prematurely each year because of obesity. However, a recently revised statistical model of that same data brought down the death toll from all categories of obesity from 400,000 to 112,000. At the same time, being mildly or moderately overweight is preventing 86,000 extra deaths – while being underweight is causing 34,000 deaths. If my sums are right, fat people are living longer than their thin counterparts.
The original 1999 study made huge extrapolations from relatively small numbers of actual measurements, like election polls, and relied on self-reported heights and weights. Heavy people tend to lie about their weight. Also, it did not account for smoking habits, which have an overwhelming influence on mortality, and on the fact that mortality risk from obesity drops as people get older.
The ‘eat-almost-nothing-and-live-forever’ brigade exists on nearly as many vitamin supplements as calories. These people are following the example of the mice in an experiment some years ago, whose life-span was doubled on a starvation diet. The same does not hold true for humans.
This brings us to the health aspect. Although we all care about mortality, illness and our quality of life matter a great deal to us, too. The US Health department states confidently that excess body weight leads to a higher risk of premature death, type 2 diabetes, hypertension, high cholesterol, cardiovascular disease, respiratory dysfunction, gout, osteoarthritis, and certain kinds of cancers. As the prevalence of adult obesity has roughly doubled in the USA since 1980, deaths from cardiovascular disease and stroke have almost halved, though deaths caused by diabetes have risen somewhat. A vast bank of treated disease is not accounted for. Certainly, modern medicine is becoming more effective at dealing with certain life-threatening complications of obesity. Alternatively, a fat store in our bellies or buttocks may tide us through hard times and the sickbed when we get older. Having a nutritional reserve seems to make people more resilient if they are hospitalized.
It is through type 2 diabetes that obesity seems to pose the biggest threat to our health. However, a large rise in obesity in the 1990s was not associated with a similar rise in diabetes. The incidence of type 2 diabetes was shown in a 2001 study to decrease significantly after weight loss of between 2.7 and 5.6kg. However, a later study showed an equally impressive reduction with 2.5 hours of weekly walking, independent of dietary factors and BMI.
Recent articles have likened insulin resistance to cardiovascular disease, much more strongly than cholesterol. We are told by experts that anyone at high risk of heart disease – and that includes a large proportion of adults – should lower their cholesterol to a level so low that it cannot be achieved by diet or exercise alone, and so we have to resort to cholesterol-lowering drugs. Last year, Americans spent $26 billion on these drugs. The counter-argument insists that it is not cholesterol per se that is the culprit, but its oxidation.
Overweight subjects are slightly more prone to colon cancer, prostate cancer and post-menopausal breast cancer, which are not major killers. Yet these people are also significantly protected against lung cancer, which is by far the most common lethal malignancy, even after the effects of smoking are subtracted.
So, what are we to glean from this maze of information and revolving medical news? Certain facts still hold firm, such as the significant detrimental effects on health and longevity of smoking and gross obesity. Secondly, diabetes-related deaths are still on the rise and it would be pertinent to reduce our intake of refined carbohydrates and to take regular exercise. What is emerging is that it is all right to be mildly overweight, and it is disadvantageous to be underweight. Medicine has been shown to effectively stave off the curtailment of life expectancy from obesity-related complications, but I would much rather avoid such problems than acquire them and then have to undergo treatment, even if my life expectancy were to remain unaltered. It would certainly be more pleasant to be able to get around and enjoy life to the full than to be immobilized, short of breath, lethargic, or in pain and forced to take regular medication. I believe we are heading towards a more sane approach to weight and my advice is to avoid major changes in dietary habits based on the latest report or fad. We have not seen the end of this story yet.