Any explanation of the root causes of the current obesity epidemic must account for its sudden appearance. Six million American adults are now morbidly obese (BMI 40+), almost twice as high as 1980 severe obesity rates, while another 9.6 million have a BMI of 35-40. The percentage of overweight children 6-11 has nearly doubled since the early 1980's. (Source: US Census 2000; NHANES III data estimates). Thus genetic causes are unlikely to be significant. Because while a predisposition to obesity can be inherited, the fact that obesity has increased so much in the last few decades appears to discount genetics as a major main cause. Also, the fact that each succeeding generation is heavier than the last indicates that changes in our environment are playing the key role.
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Overconsumption - A Possible Root Cause
Eating too many calories for our energy needs must be a major candidate for the main cause of the modern obesity epidemic. According to Dr. Marion Nestle, Professor and Chair of the Department of Nutrition and Food Studies at New York University, US agribusiness now produces 3,800 calories of food a day for every American, 500 calories more than 30 years ago — but at much lower per-calorie costs. Increases in consumption of calorie-dense foods, as evidenced by the growth of fast-food chains and higher soft drink consumption, also point to a higher energy-intake.
Eating Too Many High-Fat or Refined Sugary Foods
The type of food eaten may also play an important role in the rise of obesity. Researchers continue to discover more metabolic and digestive disorders resulting from overconsumption of trans-fats and refined white flour carbohydrates, combined with low fiber intake. These eating patterns are known to interfere with food and energy metabolism in the body, and cause excessive fat storage. Associated health disorders include insulin resistance, type 2 diabetes as well as obesity. Incidence of these "modern" diseases is increasing worldwide.
Reduced Energy Expenditure - A Possible Root Cause
People who eat more calories need to burn more calories, otherwise their calorie surplus is stored as fat. For example, if we eat 100 more food calories a day than we burn, we gain about 1 pound in a month. That’s about 10 pounds in a year. Over two decades this energy surplus causes a weight gain of 200 pounds!