Diabetes Forecast

Obesity and Type 2 Diabetes

By Erika Gebel, PhD , , ,

They're often mentioned in the same breath, but type 2 diabetes and obesity are, of course, not the same thing. Roughly one third of obese people will never develop diabetes, and 15 percent of those with type 2 diabetes are normal weight. Still, there's such a strong association between the conditions that they've sometimes been referred to with a single term: "diabesity." Being very heavy raises the risk for a host of health problems, including type 2, heart disease, cancer, sleep apnea, and arthritis.

Obesity has become far more common over the past few decades in the United States and around the world. A full third of Americans are obese and another third overweight. The scale of the epidemic is evidence of how difficult it is for many people to maintain a healthy body weight in the current environment of processed foods, big meal portions, and too few opportunities for exercise. But there are proven ways to lose pounds. Here are the basics on obesity, its causes, and slimming solutions.

Growing Waistlines

Obesity usually stems from a combination of genetic and environmental factors. The children of obese people are 10 times as likely to be obese as the offspring of trim parents, studies show. Some bodies are just genetically programmed to burn fewer calories, like a fuel-efficient car, and store the extra ones as fat. This efficiency is advantageous when food is scarce, a situation often faced by our hunter-gatherer ancestors. But in a land of plenty, it leads to plenty of weight gain.

The striking increase in obesity levels is most likely also due to changes in the environment and society. Conventional wisdom blames such things as fast food that goes right to our waistlines and video games that keep us on the couch, but researchers haven't really figured out with scientific certainty the causes of the epidemic.

Scientists do know that to gain weight, people need to eat more calories than they burn. The spread of obesity could thus stem from an increase in food consumption, a decrease in physical activity, or both. A recent article in the journal PLoS One found evidence that people burn fewer calories on the job than they did 50 years ago, which is enough alone to account for the growth in American waistlines over that time. Plus, calories are cheaper today than in the past, making overeating more affordable than ever.

Some groups are more likely to be obese than others, including former smokers, people with low incomes, and those with mental disorders or disabilities. And, of course, people who rarely exercise or move around tend to weigh more.

A Healthy Weight

Health experts put bodies into four weight categories: underweight, healthy, overweight, and obese, with the heaviest people known as morbidly obese. The scale that is typically used to divide them is the body mass index (BMI), which is based on weight and height and correlates with how much body fat a person has. Body fat can be measured directly, but it's rarely done in doctors' offices.

People with BMIs of less than 18.5 are considered underweight, 18.5 to 24.9 healthy, 25 to 29.9 overweight, and 30 and above obese (chart, left). A 6-foot-tall man who weighs 200 pounds has a BMI of 27.1; a 5-foot, 4-inch, 145-pound woman has a BMI of 24.9. There are plenty of online tools to calculate BMI; click here for a BMI calculator from ADA's Website. (The formula for BMI is weight in kilograms divided by height in meters squared.) To do the figuring yourself, multiply your weight in pounds by 703, divide that answer by your height in inches, and then divide it again by your height.

BMI is a good way to estimate health as it relates to weight, but it is far from perfect. Differences in body composition can skew results. Well-muscled people can have high BMIs despite low body fat. And the BMI's relationship to health can differ by race or ethnicity. For example, people of Asian heritage tend to get diabetes at a lower BMI than other groups, possibly because they have more body fat. To get a more accurate idea of whether a person is at a healthy weight, doctors may measure waist circumference or waist-to-hip ratio.

Down to Size

The recipe for shedding pounds is simple, even if the execution is not: Burn more calories than you consume. In short, eat less and move more.

The key to losing weight by changing eating habits is being able to sustain the new lifestyle. Weight lost on extremely low-calorie "crash" diets is likely to come back, while pounds dropped slowly and steadily may stay off for good. Plus, eating too few calories is linked to problems like gallstones, vitamin deficiencies, and fatigue. Keeping a food journal, seeing a dietitian, and finding ways to deal with stress besides snacking or overindulging may all improve the way one eats.

Whether or not exercise helps people lose weight is surprisingly controversial, but most experts agree that working out is, at the least, essential for weight maintenance. Exercising increases energy expenditure, of course, but it may also trigger the desire for post-workout snacks or bigger meals. That kind of compensatory eating negates any calories burned. Even so, physical activity offers extra benefits for people with diabetes; for one, building muscle improves blood glucose control.

If lifestyle changes aren't doing the trick, obese people and their doctors may consider other options like weight-loss medication or bariatric surgery. Orlistat (Alli, Xenical) is the only antiobesity medication currently available that is approved for long-term use. The two most popular types of weight-loss surgery are adjustable gastric banding and gastric bypass surgery, both of which can lead to a significant loss of excess body weight. Gastric bypass surgery, by reconfiguring the digestive tract, results in remission of type 2 diabetes in most patients independent of weight loss. Gastric banding helps with blood glucose control, too, but this is due to weight loss.

For all but the heaviest people, dramatic weight loss may not be necessary to promote better health. For example, losing just 5 to 7 percent of body weight is an effective way to prevent type 2 diabetes in people with prediabetes. Research has shown that this amount of weight loss is achievable and sustainable through diet and exercise. Change is never easy, but trimming down obese frames leads to tangible rewards. A longer, healthier life is worth the effort.



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