Basic information for topics, such as “What is it?” is available in the About Obesity and Overweight section. Answers to other frequently asked questions (FAQs) specific to obesity and overweight are in this section.
In adults, having overweight or obesity increases the risks for several problems, including1,2:
- Coronary heart disease
- Type 2 diabetes
- Certain types of cancer
- High blood pressure (hypertension)
- Unhealthy levels of certain types of blood fats, such as high total cholesterol or high levels of triglycerides
- Liver and gallbladder disease
- Sleep apnea and respiratory problems
- Osteoarthritis, a breaking down of cartilage and its underlying bone within a joint
- Gynecological problems, such as infertility
Overweight and obesity also increase the health risks for children and teens. For example, type 2 diabetes once was rare in American children, but the number of children with it today has grown rapidly. Early onset of type 2 diabetes can cause the early onset of complications such as vision loss, nerve damage, and cardiovascular disease.3
Some of the possible effects of children having obesity include:4
- High blood pressure and cholesterol
- Liver disease
- Sleep apnea and other lung-related problems
- Problems related to bone development
- Early onset of menstruation for girls
- Increased risk of cardiovascular disease in adulthood
In addition, children who have overweight are more likely to have overweight or obesity as adults.
Many studies have highlighted the link between obesity and infertility in women. For example, having obesity can contribute to problems with ovulation and irregular menstrual periods. It also contributes to some miscarriages and to a lowered response to fertility treatments. Research indicates that reducing obesity improves women's reproductive health.5
Women with a condition called polycystic ovary syndrome (PCOS) are at higher risk for obesity and infertility. Lifestyle changes, such as losing weight, can trigger body changes that facilitate conception in women with PCOS.6,7Learn more about PCOS.
Obesity in men also is associated with a higher risk of infertility. Excess weight may affect a man's fertility in different ways, such as through changes in his hormone and semen production.8
How much a woman weighs when she gets pregnant and how much weight she gains during pregnancy can affect her health and that of her baby. Entering pregnancy with a normal body mass index (BMI) and gaining weight within the recommended levels during pregnancy are important ways to promote a healthy pregnancy.9
The Institute of Medicine recommends the following ranges of weight gain during pregnancy for women in the United States:
- Those women who have underweight (BMI of less than 18.5) should gain 28 to 40 pounds.
- Those who have normal weight (BMI of 18.5 to 24.9) should gain 25 to 35 pounds.
- Those who have overweight (BMI of 25 to 29.9) should gain 15 to 25 pounds.
- Those who have obesity (BMI greater than 30) should limit weight gain to 11 to 20 pounds.9
NICHD research shows that gaining more weight during pregnancy than recommended increases the risk for complications.
The institute’s Healthy Pregnancy for Every Body initiative encourages plus-size pregnant women and their healthcare providers to work together to promote healthy pregnancies and births. The effort explains that BMI is just one aspect of a healthy pregnancy plan, and should not be the sole focus of a plus-size pregnant woman’s care.
- Centers for Disease Control and Prevention. (2012). Overweight and obesity: Causes and consequences. Retrieved August 8, 2012, from https://www.cdc.gov/obesity/adult/causes.html
- National Heart, Lung, and Blood Institute. (2012). What are the health risks of overweight and obesity? Retrieved August 8, 2012, from
- Hannon, T. S., Rao, G., & Arslanian, S. A. (2005). Childhood obesity and type 2 diabetes mellitus. Pediatrics, 116(2), 473–480.
- Han, J. C., Lawlor, D. A., Kimm, S. Y. (2010). Childhood obesity. Lancet, 375, 1737–1748.
- Zain, M. M., & Norman, R. J. (2008). Impact of obesity on female fertility and fertility treatment. Women's Health, 4, 183–194.
- Legro, R. S. (2007). Pregnancy considerations in women with polycystic ovary syndrome. Clinical Obstetrics and Gynecology, 50, 295–304.
- Kiddy, D. S., Hamilton-Fairley, D., Bush, A., Short, F., Anyaoku, V., Reed, M. J., et al. (1992). Improvement in endocrine and ovarian function during dietary treatment of obese women with polycystic ovary syndrome. Clinical Endocrinology (Oxford), 36, 105–111.
- Du Plessis, S. S., Cabler, S., McAlister, D. A., Sabanegh, E., & Agarwal, A. (2010). The effect of obesity on sperm disorders and male infertility. Nature Reviews: Urology, 7, 153–161.
- Institute of Medicine. (2011). Weight gain during pregnancy: Reexamining the guidelines. Retrieved August 8, 2012, from http://nationalacademies.org/hmd/Reports/2009/Weight-Gain-During-Pregnancy-Reexamining-the-Guidelines.aspx