You can hardly open a magazine or newspaper these days without reading about the growing obesity crisis. According to the Centers for Disease Control and Prevention, 1 out of 3 adults are obese and that number is expected to grow. Sadly, kids are impacted too. In 2012, around 33% of children were classified as overweight or obese. You often hear about the health risks of being obese, that it increases the risk for a variety of health problems, but how much of an effect does it have on longevity? Ultimately that’s what counts. How much does carrying around lots of excess body fat REALLY shorten lifespan?
Does Obesity Significantly Shorten Lifespan?
A recent study carried out at McGill University Health Center and McGill University looked at the impact obesity has on longevity. To do this they used a computer database and looked at results from the National Health and Nutrition Examination Survey, a research study that began in 2003 and ended in 2010.
The results are sobering. Based on the results of this study, those who are morbidly obese cut their life short by as much as 8 years, while those who are moderately obese die an average of 6 years earlier. Even being overweight appears to shave off some time with overweight people living an average of 3 years less than their normal weight counterparts. Researchers also noted that weighing more and being overweight or obese at a younger age shortens lifespan the most.
What about the So-Called Metabolically Healthy Obese?
Years ago, a study suggested that up to a third of obese people, mostly young people, are “metabolically healthy,” meaning they don’t appear to suffer from the metabolic issues that other obese people do. Obesity is commonly associated with insulin resistance and low-grade inflammation that, over time, increases the risk for health problems like heart disease and type 2 diabetes.
Why would some obese people seemingly be immune to metabolic issues? When researchers looked at the fat cells of obese men and women without metabolic issues, they found this population had more fat cells and the fat cells were smaller. In contrast, metabolically unhealthy obese people had fewer fat cells, but the fat cells they had tended to be large and engorged with inflammation. At a deeper level, they found the energy-producing organelles inside cells called mitochondria weren’t functioning properly. As a result, energy production and fat breakdown were impaired. It’s not clear whether the mitochondria malfunction leads to the inflammation or whether inflammation itself damages these energy producers organelles that are so essential for a healthy metabolism.
Are there two types of obesity – one that’s less unhealthy than the other? Probably not. More recent research shows even metabolically healthy obese men and women eventually go on to develop metabolic issues. These folks may not suffer from the same metabolic problems most obese people have but they tend to develop them over time.
In a study published in the International Journal of Obesity, researchers followed over 900 metabolically healthy obese subjects for over 10 years. By the end of the study, almost half of the participants had become unhealthy from a metabolic standpoint and a significant percentage now met the criteria for metabolic syndrome. So, the idea that you can be healthy long-term if you’re obese doesn’t necessarily hold true.
Even though men and women who are obese may have a period of metabolic health, especially when they’re young, “hidden” damage to blood vessels may be taking place. A study published in the Journal of the American College of Cardiology in 2014 showed metabolically healthy obese adults have a higher prevalence of early-stage coronary artery disease relative to normal weight adults. This suggests that even during periods when obese people don’t have obvious metabolic issues, damage to their heart and blood vessels may still be taking place.
Why Does Obesity Lead to Metabolic Problems?
Metabolic problems are usually related to chronic inflammation and insulin resistance – but where does the inflammation actually come from? For one, fat cells produce hormones that when released into the bloodstream trigger inflammation. Fat cells aren’t just sacs that store fat: they’re more like endocrine organs that produce hormones that affect whole body function.
Another theory has to do with the limited ability of fat cells to store more fat. Once the capacity for an individual fat cell to store fat is exceeded and the cells are “stretched” beyond their capacity, extra fat has to go somewhere else. One place it goes to the liver, where it contributes to fatty liver, a common form of non-alcoholic liver disease, and to muscle tissue where it’s a contributor to insulin resistance.
Obesity: A Major Risk Factor for Disease
The take-home message? Obesity not only shortens lifespan, but it also increases the risk for a long list of health problems: hypertension, stroke, coronary artery disease, type 2 diabetes, some types of cancer, osteoarthritis and sleep apnea. Lots of reasons to avoid putting on excess body fat!
The small percentage of people who are obese and metabolically healthy probably won’t stay that way unless they lose weight. Plus, even the metabolically healthy obese seem to have a higher rate of sub-clinical heart disease. The argument that obesity isn’t unhealthy in all cases seems to be more of a myth than fact.
Sadly, obesity has the power to shorten lifespan – and not an insignificant amount based on research. Plus, if you combine being obese with other bad lifestyle habits like lack of exercise and a poor diet, who knows how more lifespan may be shortened.
Tackling obesity is one of the greatest health challenges of our time and one that won’t be easily conquered. Although genetics is a factor for some people, lifestyle is a factor we can control. That’s why it’s important to get the word out – eating right and staying physically active matter. Spread the word!
On Fitness. March/April 2015. page 19.
Centers for Disease Control and Prevention. “Adult Obesity Facts”
Centers for Disease Control and Prevention. “Childhood Obesity Facts”
Journal of the American College of Cardiology. Volume 63, Issue 24, June 2014. (2014)
International Journal of Obesity advance online publication 4 November 2014; doi: 10.1038/ijo.2014.176
Diabetes Care. 2013 Aug;36(8):2388-94. doi: 10.2337/dc12-1971. Epub 2013 Mar 14.
Well. “The Healthy Obese and Their Healthy Fat Cells” October 9, 2013.
National Institutes of Health. “What Are the Health Risks of Overweight and Obesity?”
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