Last week’s New England Journal of Medicine gave us some remarkable news, via the JUPITER Trial, adding additional evidence to the pile of articles on the cardioprotective effects of statins. This article is getting lots of press, which is great, but I’d hate to see this week’s edition of the Journal get lost. Specifically, there’s a huge population-based study on obesity and mortality. We’ve explored previously the dangers of obesity, and we’ve been fought the whole way by various denialists.
Earlier studies have shown associations between excess body weight (as measured by body mass index (BMI)) and death, but this study did a few things differently. The latest study in the Journal, titled “General and Abdominal Adiposity and Risk of Death in Europe”, takes a look at a larger data set, and takes a closer look at different measures of obesity.
It has been observed for quite some time that all fat is not the same. You can take whatever aesthetic stance you wish on big butts and ample thighs, but from a health standpoint, it’s the big belly that does you in. So-called central (or truncal) obesity has many health consequences, and traditional measures of obesity may overlook this. BMI makes no distinction between types of fat, but waist circumference certainly does. The European study looked at BMI and waist measurement. Obesity defined by either one was correlated with increased risk of death, but increased waist circumference was associated with increased risk even at lower BMIs.
So, the evidence is pretty clear that belly fat is bad. But why?
There are two ways to grow fat—either by making more fat cells (adipocytes) or increasing the size if individual adipocytes. It turns out that small adipocytes and large adipocytes are metabolically very different creatures. Large adipocytes are a feature of belly fat. They tend to produce abnormally large amounts of free fatty acids. These free fatty acids contribute to the insulin resistance seen in obesity. As tissues become more resistant to the effects of insulin, insulin levels rise, and eventually, the islet cells of the pancreas begin to fail, leading to type II diabetes (which is often a combination of insulin resistance and islet cell failure). Adipocytes release various cytokines such as TNF-alpha, which lead to a pro-inflammatory and hypercoaguable state. It’s long been known that coronary heart disease, the number one killer in the U.S., is at least partly an inflammatory disease. It’s not simply that cholesterol builds up plaques in coronary arteries, but that there is active inflammation leading to plaque destabilization. And here it comes full circle.
One way to measure the general level of inflammation is via C-reactive protein (CRP). Several studies have found a relationship between elevated CRP levels and increased coronary risk, a risk that is independent of cholesterol levels. The JUPITER trial released last week look at this relationship, and appears to show that when statins are used to lower CRP levels, cardiac risk is also lowered.
The last several years have seen rapid growth in our knowledge of obesity and fat, including the discovery of leptins, and possible drug therapies involving the endocannabinoid system (although that’s not going so well at the moment).
Abdominal obesity leads to higher cholesterol, higher insulin and glucose levels, and increases inflammation and blood clotting. Even without its other problems, such as high blood pressure, sleep apnea, and obesity-hypoventilation syndrome, having a big belly is a big risk. We need to take a more proactive approach to helping the rotund become more svelte.
Pischon, T., Boeing, H., Hoffmann, K., Bergmann, M., Schulze, M.B., Overvad, K., van der Schouw, Y.T., Spencer, E., Moons, K.G.M., Tjonneland, A., Halkjaer, J., Jensen, M.K., Stegger, J., Clavel-Chapelon, F., Boutron-Ruault, M.-C., Chajes, V., Linseisen (2008). General and Abdominal Adiposity and Risk of Death in Europe New England Journal of Medicine, 359 (20), 2105-2120
D HASLAM, W JAMES (2005). Obesity The Lancet, 366 (9492), 1197-1209 DOI: 10.1016/S0140-6736(05)67483-1
Kenneth F. Adams, Ph.D., Arthur Schatzkin, M.D., Tamara B. Harris, M.D., Victor Kipnis, Ph.D.,, Traci Mouw, M.P.H., Rachel Ballard-Barbash, M.D., Albert Hollenbeck, Ph.D., and Michael F. Leitzmann, M.D. (2006). Overweight, Obesity, and Mortality in a Large Prospective Cohort of Persons 50 to 71 Years Old New England Journal of Medicine, 355 (8), 763-778