The effects were worse for younger people. Smokers were excluded from the analysis.
A massive meta-analysis pooling data from millions of people in several countries reaffirmed that body mass index (BMI) has a J-shaped relationship with mortality, with the lowest death rates among those in the traditional "normal" range of 20-25.
The study of nearly four million people revealed that those in every BMI category above and below the normal range had significantly higher mortality rates.
Yes, the analysis was based on BMI (body mass index), which can be an inaccurate marker of obesity— mostly in people with high lean body mass (muscles) for their height. Generally, for people with 40% body fat and greater, BMI does just fine. That's not a point often admitted amongst those slamming BMI as a marker, but it is the truth. Plus, as this is a study making population comparisons, BMI actually is the appropriate, if imperfect, variable to compare.
This analysis pooled 239 studies across 32 countries and included about 1.6 million deaths. Only data from large, prospective studies was included, and only studies performed after 1970 were included. The hazard ratios of all-cause mortality were generally similar across different continents, though the risk was higher for underweight and for the highest class of obesity in Europe than in East Asia.
Risks of other conditions increase too: type two diabetes, cardiovascular disease, high blood pressure, etc. (Remember: I am not any kind of medical professional.) If you're happy being obese, then I'm happy for you. But there are consequences for remaining that size.
Using two separate samples from the study — one of about 9,000 people and one of about 12,500 — researchers looked at aging adults over a six-year period. They had information on study participants' BMI, inflammation and cognition, and they found the same outcome in both samples.
"The higher participants' body mass at the first time point in the study," Bourassa said, "the greater the change in their CRP levels over the next four years. CRP stands for C-reactive protein, which is a marker in the blood of systemic inflammation in your body. Change in CRP over four years then predicted change in cognition six years after the start of the study. The body mass of these people predicted their cognitive decline through their levels of systemic inflammation.