Your friend should book an appointment with an endocrinologist to verify that opinion. In truth, the vast majority of people who are overweight have normal metabolisms, so they can’t blame their waistlines on their thyroid glands. What they lack is an accurate eye for portion size. People consistently underestimate their food intakes and overestimate their exercise; the more overweight they are, the more they fudge the numbers, underestimating by as much as 800 calories a day. According to the latest USDA statistics, Americans averaged 300 calories more every day now than they did back in 1985. That’s a hefty calorie increase that easily explains why weight problems are on the rise.