 In the ABCs of health consequences of obesity, I is for immunity. The SOS trial, which followed the fate of thousands of bariatric surgery patients for a decade or two compared to a control group that maintained their weight, and those who surgically lost about 20% of their body weight not only lived longer, thanks in part to less diabetes and less cardiovascular disease, but they also got less cancer. This may be because anti-tumor immunity appears to be affected by weight. Natural killer cells are your immune system's first line of defense against cancer cells, as well as many viral infections, and their function is severely impaired in obesity. Randomized obese individuals to a weight loss program, though, and there was a significant reactivation of their natural killer cell function within just three months. The program involved an exercise component, though, and so it's hard to tease out the impact of the weight loss itself, since physical activity alone can boost natural killer cell activity. On the other end of the immune spectrum, obesity is suspected to be a causal risk factor for the development of the autoimmune disease multiple sclerosis. This suggests obesity is associated with the worst of both worlds when it comes to immune function, under activity when it comes to protecting against cancer and infection, but over activity when it comes to certain inflammatory autoimmune conditions. J is for jaundice. Thanks to the obesity epidemic, non-alcoholic fatty liver disease is now the most common liver disorder in the industrialized world. Fat doesn't just end up in our belly and thighs, but inside some of our internal organs. More than 80% of individuals with abdominal obesity may have fatty infiltration into their liver, and those with severe obesity, the prevalence can exceed 90%. This can lead to inflammation, scarring, and ultimately cirrhosis and liver cancer. Currently, this non-alcoholic fatty hepatitis is the leading cause of liver transplants in American women, and men are expected to catch up in 2020. K is for kidneys. Obesity is one of the strongest risk factors for chronic kidney diseases. Well, your kidneys compensate for the metabolic demands of the excess weight by redlining to what's called hyperfiltration to deal with the extra workload. This resulting increased pressure within the kidneys can damage the sensitive structures and increase the risk of kidney failure over the long term. What about LMNOP through Z? If you want to continue through the alphabet, L could be diminished lung function, M for metabolic syndrome, and so on. There's even an X for zyphodenia, pain at the tip of the bottom of the breast bone from being bent forward by an expanding abdomen. Given the myriad health conditions associated with excess weight, annual medical spending attributable to obesity is nearly $2,000 per year, with obese workers with multiple conditions, costing companies up to $10,000 more in health care coverage compared to lean counterparts. This may actually account for some of the wage gap that obese employees experience as companies try to pass along these costs beyond just brazen discrimination. Between health care costs and diminished productivity, in terms of lost workdays, the total lifetime cost of obesity for children and teens has been estimated to exceed $150,000. Some estimates beg the national cost of obesity, about $150 billion, with another $50 billion per year added by 2030, as our increasingly heavy baby boomers continue to age. Others diametrically disagree, based on the morbid fact that obese individuals may not live as long, just as the medical costs of tobacco-related diseases may be more than offset by the shortened survival of smokers. The lifetime health care costs of obese individuals may turn out to be lower because they're expected to die so much sooner. So the true cost may be more in lives rather than dollars. How much does being overweight cut your life short? I'll explore just that question next.