How common is overweight or obesity and what is the cause?

Almost 70% of American adults are overweight or obese (CDC 2008). The specific terms overweight and obesity are conditions that involve an excess of body fat.  Specifically, the term overweight means a body mass index (BMI=wt/ht2) of 25 or more and obese is a BMI of 30 or above.  These conditions are caused by the consumption of more calories than the body uses. In other words, when people eat more calories than they burn they will gain body fat. The type of calories do not matter when it comes to weight gain. Too much protein, carbohydrates, fats, or alcohol will increase body fat.

BMI Table1

BMI Weight
18.5-24.9 Normal
25-29.9 Overweight
30 Obese


Although BMI is not a precise way to measure body fat, it is an accurate way to identify excess weight in sedentary people.  The only time BMI is inaccurate is when it is used on bodybuilders or people who lift heavy weights frequently because they have a large amount of muscle.  A more precise way to measure body fat involves machines that analyze what percent of the body is muscle versus fat.  When this kind of evaluation was done on American adults, it turned out women were 40% fat and men were 28% fat. (St-Onge 2010)  In fact, even the normal weight adults with a BMI below 25 had a lot of body fat.  Normal weight women were 34% fat while men were 23% fat. (St-Onge 2010)  To give you an idea of how high that is, I have a body fat of 20% and my husband has 17% body fat and neither of us is an athlete.  We both go to the gym about twice a week on average and sometimes once a week.  I often see women who appear thin but actually have a relatively high amount of body fat. For example, one of my friends is the same height and weight as me and seemingly thin.  Her body fat was 30% though compared to my 20% when we used a body fat scale a few years ago. This is because I have more muscle mass than she does and it really goes to show that women need to lift weights more often.  Women have less muscle than men so their body fat percent will usually be higher. The only way to change this is with the right combination of diet and exercise.

Overweight or obesity increases your risk of:

  • Heart attacks
  • Strokes
  • Diabetes
  • Cancer (Breast/Colon/Endometrial)
  • Hypertension
  • Metabolic Syndrome
  • Sleep apnea
  • Respiratory problems
  • Osteoarthritis
  • Infertility
  • Menstrual problems
  • Liver disease
  • Gallbladder disease

(CDC 2011)


Is overweight or obesity preventable?

Yes, exercising daily and eating plenty of fresh fruits and vegetables can help prevent overweight and obesity. But small changes only offer small results. If you have a long way to go before reaching a healthy weight then major weight loss will require major lifestyle changes.


1. Division of Nutrition, Physical Activity and ObesityNational Center for Chronic Disease Prevention and Health Promotion   www.cdc.gov

2. http://www.cdc.gov/obesity/causes/health.html

3. St-Onge MP. Are normal-weight Americans over-fat? Obesity (Silver Spring). 2010 Nov;18(11):2067-8.