Obesity Paradox
A number of studies over the past decade have suggested better mortality rates in people over the age of 50 carrying a bit of extra weight. For most of us in the health industry and the general public, this appears counterintuitive.
Let’s examine some of the evidence. There have been a variety of studies, mainly meta-analyses, which have suggested an inverse link between body weight and health. 40 cohort studies of just over 250,000 participants demonstrated a 13% reduction in all cause death & a 12% reduction in cardiovascular death in overweight patients i.e. BMI between 25 to 30. There were no differences in the death rates between normal weight people (BMI 20 to 25) and Grade 1 obese people (BMI 30 to 35). In this particular study, however, once the BMI rose above 35, there was an 88% increase in death risk.
A very large meta-analysis of 2.9 million people from 97 trials showed a 6% reduction in death in overweight people when compared with normal weight and Grade 1 obesity.
The benefits are even more striking in hypertensive patients, with a reduction in death, heart attack, stroke of 23% in overweight patients and strangely a 32% reduction in those with Grade 1 obesity and a 24% reduction in those with higher grades of obesity compared with people who are normal weight.
Another study from Holland followed patients for seven years after coronary stenting and demonstrated those who had a BMI between 27.5 up to 30 had a 41% reduction in death.
The benefits of being overweight are also demonstrated for people with heart failure, peripheral arterial disease, stroke, previous history of thrombo-embolism, post coronary bypass grafting, atrial fibrillation, death rates in intensive care, general surgery, type II diabetes, chronic obstructive pulmonary disease, haemodialysis, critically ill patients and those with osteoporosis.
Doctors are always encouraging their patients to lose weight and the reality is that most people are spectacularly unsuccessful in doing so. Although it is my strong belief that it is important for us to keep our weight down to healthy levels, it certainly appears that there is a significant difference between a healthy weight before the age of 50 and over the age of 50.
As anyone over the age 50 reading this article will fully appreciate that once your hormones go south, whether you’re male or female, it is much more difficult to keep the fat down, especially off your belly. It may well be that obese patients with more severe abdominal obesity and visceral fat died earlier and therefore skewed the data compared with those with less risky lower body obesity. Interestingly, the accumulation of visceral fat is much greater in age group 35 to 45 with an average 52% increase, compared with 55 to 65 with only 7% and for those older than 65, 11%.
So, are there any adequate explanations for this so-called obesity paradox? The first and rather obvious explanation is what we call reverse causality. It is a well-established fact that the sicker patients tend to lose more weight than those who have mild disease. Thus, it is not the obesity that is protecting people rather the loss of weight occurring as a consequence of a more severe illness. Secondly, those people who are carrying less weight with established illnesses such as cardiovascular disease, cancer, osteoporosis and type II diabetes, tend to have a stronger genetic predisposition to the disease. Could it be, therefore, the more genetic an illness, the more seriously it affects the body compared with lifestyle associated disease, which tends to be associated with obesity?
Another explanation is that smokers tend to be thinner than non-smokers but also suffer more serious diseases.
In the specific case of chronic kidney disease this is a chronic inflammatory state and also associated with protein energy wasting. There is a paradoxical association between traditional risk factors & cardiovascular disease in this setting and the weight loss itself may be a marker of more severe disease.
Also, BMI is not as good a marker for abdominal fat as waist circumference and it may be that those with the higher BMI have a larger muscle mass, which is felt to be protective. Also, there is the consideration of being fat but fit which may include better cardiovascular and muscle strength.
It is my strong belief that we should all try and maintain a healthy body weight but over the age of 50, I would suggest you should be aiming for a BMI between 25 to 30 with the waist circumference around 90 to 95 for a male and 75 to 80 for a female. I advise all my patients beyond the age of 50 to focus more on healthy eating which is basically to eat less and eat more naturally, along with maintaining 3 to 5 hours of testing exercise per week which should include two thirds cardio and a third resistance training. This is much better for your health than obsessing about weight.
