The research results here are from the latest in a line of epidemiological studies to firmly refute the obesity paradox, burying it with more data and better study design, to show that excess weight is very definitely harmful to health and longevity. The obesity paradox was the idea that excess weight – meaning excess fat tissue – could be protective in some circumstances in older individuals, such as in the case of cardiovascular disease. It arose from the combination of (a) flawed study design and (b) human nature. There are a lot of overweight and obese individuals in the world today because technological progress has greatly reduced the cost of calories. As a result more people consume significantly more calories than was the case in even comparatively recent history, and that has the natural consequence of excess fat tissue. People who are overweight, just like all other individuals, tend to want to hear comforting things about their present state. Hard truths are called hard truths for a reason. Thus the incorrect research results, while being widely attacked and then debunked within the scientific community, nonetheless received a great deal of attention from the public at large simply because they said what people wanted to hear.
Unfortunately, excess visceral fat tissue is harmful. The more of that fat tissue carried and the longer it is carried, the greater the negative impact on risk of age-related disease, quality of life, and life span. The more fat tissue, the greater the lifetime medical expense, even as the expected length of life is shorter. Stepping away from epidemiology, the recording of outcomes, to look at the biochemistry of fat tissue, it becomes ever more clear that it would be highly counterintuitive for any overall health benefit to derive from a large amount of visceral fat. Fat tissue generates chronic inflammation through a variety of mechanisms, including generation of senescent cells, and in this way directly accelerates many of the aspects of aging.
How did the original studies – those finding excess weight to be protective – arrive at the incorrect conclusion? Primarily, the researchers failed to account for the weight loss that tends to occur in the more severe stages of age-related disease. Older people who are thin fall into two camps. The first camp have been thin their whole lives, and are comparatively healthy. The second camp have been overweight for much of their lives, and have only recently lost that weight due to the progression of illness. They are comparatively unhealthy and experience higher mortality rates. Without separating out these groups, the ill, thin people greatly distort the overall picture of weight in later life. The open access paper here adds another mechanism that can help to explain the issue, in that obese and overweight individuals appear to be diagnosed with heart disease at earlier stages than is the case for thin people. This breaks some of the assumptions baked into earlier studies regarding duration of illness and time to mortality
read the rest of this article published on 28 February – Fight Aging!