Obesity tends to shorten lifespan, mostly due to higher rates of cancer and cardiovascular disease like heart attacks and strokes. Doctors and dietitians recommend loss of excess weight all day long, figuring it will reduce the risk of obesity-related death and disease. That’s not necessarily the case, however. It’s called the “obesity paradox“: some types of overweight and obese patients actually seem to do better (e.g., live longer) if they’re above the so-called healthy body mass index of 18.5 to 24.9. For instance: those with heart failure, coronary artery disease, and advanced kidney disease.
It’s never really been clear whether the average obese person (body mass index over 30) improves his longevity by losing some excess weight. That’s what the study at hand is about.
Baltimore-based investigators followed the health status of 585 overweight or obese older adults over the course of 12 years. Half of them were randomized to an intentional weight loss intervention. All of them had a high blood pressure diagnosis. Average age was 66. Average body mass index was 31. Details of the weight-loss intervention are unclear, but it was probably along the lines of “eat less, exercise more.”
What Did They Find?
The weight-loss group lost and maintained an average of 4.4 kg (9.7 lb) over the 12 years of the study. This is about 5% of initial body weight, the minimal amount thought to be helpful for improvement in weight-related medical problems. Most of the weight loss was over the first three years.
The men assigned to the weight-loss program had about half the risk of dying over the course of the study, compared to the men not assigned to weight loss. The authors don’t seem to put much stock in it, however, stating that “…no significant difference overall was found in all-cause mortality between older overweight and obese adults who were randomly assigned to an intentional weight-loss intervention and those who were not.”
With regards to the men losing weight, we’re only talking about 100-150 test subjects, a relatively small number. So I understand why the researchers didn’t make a big deal of the lower mortality: it may not be reproducible.
This same research group did a similar study of 318 arthritis patients and intentional weight loss, finding a 50% lower death rate over eight years.
The authors reviewed many similar studies done by other teams, noting increased death rates from weight loss in some studies, and lesser death rates in others.
When the studies are all over the place like this, it usually means there’s no strong association either way. Nearly all the pertinent studies were done on relatively healthy, middle-aged and older folks. The most reliable thing you can say about the issue is that loss of excess fat weight doesn’t increase your odds of premature death.
Remember that patients with coronary heart disease, congestive heart failure, or advanced kidney disease tend to live longer if they’re overweight or at least mildly obese. It’s the obesity paradox. Will they live longer or die earlier if they go on a weight-loss program? We don’t know.
We do know that intentional weight loss helps:
- prevent type 2 diabetes
- maintain reasonable blood pressures (avoiding high blood pressure)
- improves lower limb functional ability
Maybe that’s enough.
Reference: Shea MK, Nicklas BJ, Houston DK, Miller ME, Davis CC, Kitzman DW, Espeland MA, Appel LJ, & Kritchevsky SB (2011). The effect of intentional weight loss on all-cause mortality in older adults: results of a randomized controlled weight-loss trial. The American journal of clinical nutrition, 94 (3), 839-46 PMID: 21775558