Join AOA banner ad
Finally A Cure for Obesity!

  American Obesity Association

Education Research Prevention Treatment Consumer Protection Discrimination

Advocacy Updates
Childhood Obesity
Contacting Congress
Tax Breaks

AOA Fact Sheets
Health Effects of Obesity
  Persons with obesity are at risk of developing one or more serious medical conditions, which can cause poor health and premature death.   Obesity is associated with more than 30 medical conditions, and scientific evidence has established a strong relationship with at least 15 of those conditions. Preliminary data also show the impact of obesity on various other conditions. Weight loss of about 10% of body weight, for persons with overweight or obesity, can improve some obesity-related medical conditions including diabetes and hypertension.

Obesity-Related Medical Conditions

The prevalence of various medical conditions increases with overweight and obesity for men and women as shown in Tables 1 and 2.

Table 1. Prevalence of Medical Conditions
by Body Mass Index (BMI) for Men
Medical Condition Body Mass Index
18.5 to 24.9 25 to 29.9 30 to 34.9 > 40
  Prevalence Ratio (%)
Type 2 Diabetes 2.03 4.93 10.10 10.65
Coronary Heart Disease 8.84 9.60 16.01 13.97
High Blood Pressure 23.47 34.16 48.95 64.53
Osteoarthritis 2.59 4.55 4.66 10.04
Source: NHANES III, 1988 - 1994.

Table 2. Prevalence of Medical Conditions
by Body Mass Index (BMI) for Women
Medical Condition Body Mass Index
18.5 to 24.9 25 to 29.9 30 to 34.9 > 40
  Prevalence Ratio (%)
Type 2 Diabetes 2.38 7.12 7.24 19.89
Coronary Heart Disease 6.87 11.13 12.56 19.22
High Blood Pressure 23.26 38.77 47.95 63.16
Osteoarthritis 5.22 8.51 9.94 17.19
Source: NHANES III, 1988 - 1994.


    Osteoarthritis (OA)
    • Obesity is associated with the development of OA of the hand, hip, back and especially the knee.
    • At a Body Mass Index (BMI) of > 25, the incidence of OA has been shown to steadily increase.
    • Modest weight loss of 10 to 15 pounds is likely to relieve symptoms and delay disease progression of knee OA.

    Rheumatoid Arthritis (RA)

    • Obesity has been found related to RA in both men and women.

Birth Defects
  • Maternal obesity (BMI > 29) has been associated with an increased incidence of neural tube defects (NTD) in several studies, although variable results have been found in this area.
  • Folate intake, which decreases the risk of NTD�s, was found in one study to have a reduced effect with higher pre-pregnancy weight.
    Breast Cancer
    • Postmenopausal women with obesity have a higher risk of developing breast cancer. In addition, weight gain after menopause may also increase breast cancer risk.
    • Women who gain nearly 45 pounds or more after age 18 are twice as likely to develop breast cancer after menopause than those who remain weight stable.
    • High BMI has been associated with a decreased risk of breast cancer before menopause. However, a recent study found an increased risk of the most lethal form of breast cancer, called inflammatory breast cancer (IBC), in women with BMI as low as 26.7 regardless of menopausal status.
    • Premenopausal women diagnosed with breast cancer who are overweight appear to have a shorter life span than women with lower BMI.
    • The risk of breast cancer in men is also increased by obesity.
    Cancers of the Esophagus and Gastric Cardia
    • Obesity is strongly associated with cancer of the esophagus and the risk becomes higher with increasing BMI.
    • The risk for gastric cardia cancer rises moderately with increasing BMI.
    Colorectal Cancer
    • High BMI, high calorie intake, and low physical activity are independent risk factors of colorectal cancer.
    • Larger waist size (abdominal obesity) is associated with colorectal cancer.
    Endometrial Cancer (EC)
    • Women with obesity have three to four times the risk of EC than women with lower BMI.
    • Women with obesity and diabetes are reported to have a 3-fold increase in risk for EC above the risk of obesity alone.
    • Body size is a risk factor for EC regardless of where fat is distributed in the body.
    Renal Cell Cancer
    • Consistent evidence has been found to associate obesity with renal cell cancer, especially in women.
    • Excess weight was reported in one study to account for 21% of renal cell cancer cases.
Cardiovascular Disease (CVD)
  • Obesity increases CVD risk due to its effect on blood lipid levels.
  • Weight loss improves blood lipid levels by lowering triglycerides and LDL (�bad�) cholesterol and increasing HDL (�good�) cholesterol.
  • Weight loss of 5% to 10% can reduce total blood cholesterol.
  • The effects of obesity on cardiovascular health can begin in childhood, which increases the risk of developing CVD as an adult.
  • Overweight and obesity increase the risk of illness and death associated with coronary heart disease.
  • Obesity is a major risk factor for heart attack, and is now recognized as such by the American Heart Association.
Carpal Tunnel Syndrome (CTS)
  • Obesity has been established as a risk factor for CTS.
  • The odds of an obese patient having CTS were found in one study to be almost four times greater than that of a non-obese patient.
  • Obesity was found in one study to be a stronger risk factor for CTS than workplace activity that requires repetitive and forceful hand use.
  • Seventy percent of persons in a recent CTS study were overweight or obese.

Chronic Venous Insufficiency (CVI)

  • Patients with CVI, an inadequate blood flow through the veins, tend to be older, male, and have obesity.

Daytime Sleepiness

  • People with obesity frequently complain of daytime sleepiness and fatigue, two probable causes of mass transportation accidents.
  • Severe obesity has been associated with increased daytime sleepiness even in the absence of sleep apnea or other breathing disorders.

Deep Vein Thrombosis (DVT)

  • Obesity increases the risk of DVT, a condition that disrupts the normal process of blood clotting.
  • Patients with obesity have an increased risk of DVT after surgery.

Diabetes (Type 2)

  • As many as 90% of individuals with type 2 diabetes are reported to be overweight or obese.
  • Obesity has been found to be the largest environmental influence on the prevalence of diabetes in a population.
  • Obesity complicates the management of type 2 diabetes by increasing insulin resistance and glucose intolerance, which makes drug treatment for type 2 diabetes less effective.
  • A weight loss of as little as 5% can reduce high blood sugar.
End Stage Renal Disease (ESRD)
  • Obesity may be a direct or indirect factor in the initiation or progression of renal disease, as suggested in preliminary data.

Gallbladder Disease

  • Obesity is an established predictor of gallbladder disease.
  • Obesity and rapid weight loss in obese persons are known risk factors for gallstones.
  • Gallstones are common among overweight and obese persons. Gallstones appear in persons with obesity at a rate of 30% versus 10% in non-obese.


  • Obesity contributes to the cause of gout -- the deposit of uric acid crystals in joints and tissue.
  • Obesity is associated with increased production of uric acid and decreased elimination from the body.

Heat Disorders

  • Obesity has been found to be a risk factor for heat injury and heat disorders.
  • Poor heat tolerance is often associated with obesity.
  • Over 75% of hypertension cases are reported to be directly attributed to obesity.
  • Weight or BMI in association with age is the strongest indicator of blood pressure in humans.
  • The association between obesity and high blood pressure has been observed in virtually all societies, ages, ethnic groups, and in both genders.
  • The risk of developing hypertension is five to six times greater in obese adult Americans, age 20 to 45, compared to non-obese individuals of the same age.
Impaired Immune Response
  • Obesity has been found to decrease the body�s resistance to harmful organisms.
  • A decrease in the activity of scavenger cells, that destroy bacteria and foreign organisms in the body, has been observed in patients with obesity.

Impaired Respiratory Function

  • Obesity is associated with impairment in respiratory function.
  • Obesity has been found to increase respiratory resistance, which in turn may cause breathlessness.
  • Decreases in lung volume with increasing obesity have been reported.

Infections Following Wounds

  • Obesity is associated with the increased incidence of wound infection.
  • Burn patients with obesity are reported to develop pneumonia and wound infection with twice the frequency of non-obese.


  • Obesity increases the risk for several reproductive disorders, negatively affecting normal menstrual function and fertility.
  • Weight loss of about 10% of initial weight is effective in improving menstrual regularity, ovulation, hormonal profiles and pregnancy rates.

Liver Disease

  • Excess weight is reported to be an independent risk factor for the development of alcohol related liver diseases including cirrhosis and acute hepatitis.
  • Obesity is the most common factor of nonalcoholic steatohepatitis, a major cause of progressive liver disease.
Low Back Pain
  • Obesity may play a part in aggravating a simple low back problem, and contribute to a long-lasting or recurring condition.
  • Women who are overweight or have a large waist size are reported to be particularly at risk for low back pain.

Obstetric and Gynecologic Complications

  • Women with severe obesity have a menstrual disturbance rate three times higher than that of women with normal weight.
  • High pre-pregnancy weight is associated with an increased risk during pregnancy of hypertension, gestational diabetes, urinary infection, Cesarean section and toxemia.
  • Obesity is reportedly associated with the increased incidence of overdue births, induced labor and longer labors.
  • Women with maternal obesity have more Cesarean deliveries and higher incidence of blood loss during delivery as well as infection and wound complication after surgery.
  • Complications after childbirth associated with obesity include an increased risk of endometrial infection and inflammation, urinary tract infection and urinary incontinence.
  • Bodily pain is a prevalent problem among persons with obesity.
  • Greater disability, due to bodily pain, has been reported by persons with obesity compared to persons with other chronic medical conditions.
  • Obesity is known to be associated with musculoskeletal or joint-related pain.
  • Foot pain located at the heel, known as Sever�s disease, is commonly associated with obesity.
  • Obesity is a predictive factor of outcome in acute pancreatitis. Obese patients with acute pancreatitis are reported to develop significantly more complications, including respiratory failure, than non-obese.
  • Patients with severe pancreatitis have been found to have a higher body-fat percentage and larger waist size than patients with mild pancreatitis.
Sleep Apnea
  • Obesity, particularly upper body obesity, is the most significant risk factor for obstructive sleep apnea.
  • There is a 12 to 30-fold higher incidence of obstructive sleep apnea among morbidly obese patients compared to the general population.
  • Among patients with obstructive sleep apnea, at least 60% to 70% are obese.
  • Elevated BMI is reported to increase the risk of ischemic stroke independent of other risk factors including age and systolic blood pressure.
  • Abdominal obesity appears to predict the risk of stroke in men.
  • Obesity and weight gain are risk factors for ischemic and total stroke in women.
Surgical Complications
  • Obesity is a risk factor for complications after a surgery.
  • Surgical patients with obesity demonstrate a higher number and incidence of hospital acquired infections compared to normal weight patients.
Urinary Stress Incontinence
  • Obesity is a well-documented risk factor for urinary stress incontinence, involuntary urine loss, as well as urge incontinence and urgency among women.
  • Obesity is reported to be a strong risk factor for several urinary symptoms after pregnancy and delivery, continuing as much as 6 to 18 months after childbirth.
  • Several other obesity-related conditions have been reported by various researchers including:
    • abdominal hernias, acanthosis nigricans, endocrine abnormalities, chronic hypoxia and hypercapnia, dermatological effects, depression, elephantitis, gastroesophageal reflux, heel spurs, hirsutism, lower extremity edema, mammegaly (causing considerable problems such as bra strap pain, skin damage, cervical pain, chronic odors and infections in the skin folds under the breasts, etc.), large anterior abdominal wall masses (abdominal paniculitis with frequent panniculitis, impeding walking, causing frequent infections, odors, clothing difficulties, low back pain), musculoskeletal disease, prostate cancer, pseudo tumor cerebri (or benign intracranial hypertension), and sliding hiatil hernia.

Note: Readers should note that researchers have not always used the same criteria to identify overweight and obesity. In this fact sheet, AOA has attempted to use the generally accepted definitions for overweight as a Body Mass Index (BMI) of 25 to 29.9 and obesity as a BMI of 30 or above. We have made an effort to identify studies which have used those specific definitions as well as other scientifically accepted measurements such as waist circumference and waist to hip ratio.

American Obesity Association
Copyright � 2002. All rights reserved.
Terms of Service
This web site was last updated on May 2, 2005.