We investigate everything you ever wanted to know about this soda alternative. Are they as healthy as they seem? What's really in them and how do they have so much flavor while being so low in calories? Plus, Health Court is in session: This woman says her best friend can't get enough of the keto diet, eating bacon and fatty foods and hurting her health. Her friend argues she's lost 30 pounds and won't turn back. Who's right?


Diet and Nutrition

What's Really Causing Your Obesity: Nature or Nurture?

It's more complex than too many calories and not enough physical activity.

The American Medical Association officially recognized obesity as a disease in 2013. But in the past 13 years, there's not been much of a shift in the understanding of what causes obesity — not in the general public, in people who contend with the condition or in the practice of medicine. Most people still think of obesity as a character flaw caused by too many calories and not enough physical activity. But it's much more complex than that.

A study analyzing National Health and Nutrition Examination Survey (NHANES) data found that even though US adults' BMI increased between 1988 and 2006, the amount of calories adults consumed and the energy they expended were unchanged. It also appears that the quality of calories consumed (low versus high glycemic index) is as important a consideration as the total quantity. And genetics only explains about 2.7% variation in people's weight, according to a study in Nature. That all adds up to this: The two most common explanations for obesity — calories in, calories out and family history — cannot, by themselves, explain the current epidemic.

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