Why Are So Many People Obese?

There is an obesity epidemic in this country. The percent of people who are overweight and obese has doubled since 1992. Now one-third of adults in the United States are obese. What has happened since 1992 to cause this obesity epidemic?

Too many calories will increase your fat. The average American in 2000 was eating 800 calories a day more than in 1950. When you eat more calories than the body can use for energy, the extra calories are used to make fat. Only a little extra food is needed to gain weight. Ten additional calories a day can add a pound of fat in a year. Although experts agree eating more is the ultimate cause for the obesity epidemic, this does not explain why the epidemic did not occur earlier. There are a number of explanations why this has happened:

Sugar

Americans increased their average sugar intake from 109 pounds in 1950 to 152 pounds in 2000. High sugar intake, particularly from sugary drinks, is associated with obesity. People drinking sugary drinks are more likely to gain weight and are more likely to maintain or lose weight if they stop. Unfortunately, switching to diet sweeteners can temporarily satisfy the body’s craving for sweet food, but may also train the body to eat more sweet food without stopping.

Addictive Combinations of Fat and Sugar

Fat and sugar combined may be addictive and lead to binge eating. When people have a choice, these rich foods are more likely to be eaten than healthy foods like green leafy vegetables. Some people even report that food companies deliberately create addictive foods to increase sales.

Available Fast Food

There are many more places to buy food. In addition to fast food restaurants, gas stations and many other types of stores also have fast food. People who eat more fast food weigh more.

Exercise

Only 21 percent of adults in the United States meet government exercise guidelines. However, this number has increased from 14 percent in 1998. Walking 200 extra steps a day burns about 10 calories a day, enough to help keep off a pound a year. Taking elevators, parking close to stores, driving short distances all decrease the amount of calories burned. The relationship between decreased exercise and gaining weight is unclear from studies, but exercise appears especially import in maintaining weight loss.

Genetics

The genetics of obesity have not been completely worked out, but there are multiple genes associated with obesity. Identical twins tend to be the same weight.

Microbiome

All of us have bacteria living in our intestine. This is called your microbiome. Your microbiome helps you digest food. If your microbiome does a poor job of digesting your food, more calories are absorbed by your body and you are more likely to gain weight. Research has linked processed, fried and fatty food with impaired functioning of the microbiome. Fresh fruits and vegetables help improve functioning of the microbiome.

Endocrine disrupters

Chemicals such as pesticides with hormone-like activity can affect people. Researchers have found evidence these can contribute to obesity.

There are many other possible factors. Other people in your social network affect your eating habits. Your baby weight affects your adult weight.

In conclusion, although eating more is the ultimate reason for gaining weight, we have multiple hypotheses about why people are eating more now than 20 years ago. It is unlikely there will be one explanation for this. Most likely, there are multiple factors including those above that are playing a role.

Selected References

1. Sugar intake – http://www.usda.gov/factbook/chapter2.pdf
2. Sugary Drinks- http://www.hsph.harvard.edu/nutritionsource/healthy-drinks/sugary-drinks/
3. Avena NM, Rada P, Hoebel BG: Sugar and Fat Bingeing Have Notable Differences in Addictive-like Behavior. J Nutr. 2009 Mar; 139(3): 623–628.
4. Making addictive food -http://modernhealthmonk.com/food-addiction/
5. Cummins S, Macintyre S: Food environments and obesity.   neighborhood or nation? Journal of Epidemiology 2006;35:100–104
6. McInnis KJ: Exercise and obesity. Review in Depth: Exercise in the modification of cardiovascular disease risk: biologic mechanisms.   Coronary Artery Disease: March 2000; 11(2): 111-116
7. Exercise and Obesity- http://www.cdc.gov/nchs/data/hus/hus14.pdf#063
8. Walley AJ, Blakemore AF, Froguel P: Genetics of obesity and the prediction of risk for health. Human Molecular Genetics.   2006 Human Molecular Genetics. 15(2): R124-R130.
9. Stunkard AJ, Foch TT, Hrubec Z: A Twin Study of Human Obesity. JAMA. 1986;256(1):51-54.
10. Turnbaugh PJ, Ley RE, Mahowald MA, Magrini V, Mardis ER, Gordon JI: An obesity-associated gut microbiome with increased capacity for energy harvest. December 2006; Nature 444, 1027-1031
11. Newbold RR, Padilla-Banks E, Jefferson WN, Heindel JJ.: Effects of endocrine disruptors on obesity. Int J Androl. 2008 Apr;31(2):201-8