Obesity: Consequences for Foot Health
The link between obesity/overweight and poor health has been documented extensively. According to the World Health Organization, worldwide obesity has nearly doubled since 1980; in 2008, 35% of adults aged 20 and over were overweight (more than 1.4 billion adults) and 11% (over 200 million men and nearly 300 million women) were obese, putting them at increased risk for a number of chronic diseases, including diabetes, cardiovascular diseases and cancer (http://www.who.int/topics/obesity/en/). A person with a body mass index (BMI) greater than or equal to 25 is overweight; a BMI greater than or equal to 30 means the person is obese.
In the United States alone, more than 78 million (about 36%) adults and 12.5 million (about 17%) children are obese, according to the Centers for Disease Control and Prevention (http://www.cdc.gov/nchs/data/databriefs/db82.pdf). A study by Wang, et.al. published in the journal Obesity in 2008 predicted that by 2030, 86% of the US population would be overweight or obese. The Institute for Preventive Foot Health (IPFH) is concerned because affected individuals not only are at increased risk for life-threatening diseases; they also are at increased risk for foot conditions, making it less likely that they will engage in the regular physical activity that could help their weight problem.
Impact on Feet
Increasing body mass index (BMI)—specifically, abdominal fat mass—is “strongly associated with foot pain and disability,” according to the authors of an article published in the journal Arthritis Care Research (2012 Feb;64(2):262-8; http://www.ncbi.nlm.nih.gov/pubmed/21972207). Other research supports these findings. For example, the National Foot Health Assessment 2012, conducted for IPFH by The NPD Group, noted a strong negative relationship between obesity and foot health: 51% of survey respondents who characterized their foot health as “fair” or “poor” reported being obese. This is in sharp contrast to those with a normal BMI (below 25) – only 21% of these respondents described their foot health as “fair” or “poor.”
Prior to this, a 2005 survey conducted by the American Orthopaedic Foot and Ankle Society found that respondents who indicated that they had foot and ankle pain also tended to have higher BMIs, as did those who said they had previously seen a physician about foot and ankle pain. According to Stuart D. Miller, MD, one of the study’s authors, “It is important for the public to know that obesity isn’t just an aesthetic issue, but a contributing cause of musculoskeletal health problems, specifically with the feet and ankles.” 1
Obesity affects not just the feet, but the entire lower kinetic chain, including the hips, knees and ankles. Research over the past 10 to 15 years shows there are three major ways in which obesity has a negative impact on the feet and lower extremities:
Higher foot pressures, gait alterations, changes in foot morphology and subsequent negative impacts on balance and mobility. Studies have shown that compensatory gait alterations are associated with obesity. Higher BMI was associated with reduced ability to move from a sitting to a standing position and with limited mobility in older patients. 2 Other studies have shown the negative impacts of obesity on walking gait stability, and its association with increased forefoot width and higher plantar pressures during standing and walking. 3,4,5,6,7
Increased forefoot pain, and increased frequency or probability of specific foot conditions. Increased BMI has been shown to be strongly associated with non-specific foot pain in the general population and with chronic plantar heel pain in a non-athletic population. 8 Another study postulated that structural changes in the feet of obese children produced discomfort that may hinder them from participating in physical activity. 9 Other studies have shown increased prevalence of gout in obese people, as well as increased probability of tendinitis, plantar fasciitis and osteoarthritis. 10,11,12,13,14,15
Risk and severity of lower limb injuries. Increased BMI is associated with increased likelihood of foot, ankle and knee fractures in children. 16 Another study suggests that obese people have a greater risk of sustaining a more proximal distal fracture of the fibula. 17 It has also been found that people with increased BMI are more prone to sustaining distal extremity injuries in general, and that obese individuals are more likely to seek treatment for osteoarthritis of the knee than those with lower BMIs. 18 According to the Canadian Joint Replacement Registry, people with BMIs of 30 to 35 are 8.5 times more likely to need total knee replacement than those with BMIs of less than 25. Additionally, people with BMIs of more than 35 are nearly 19 times more likely to need total knee replacement, while those with a BMI of 40 or higher are nearly 33 times more likely. 19 Some physicians recommend weight loss in combination with arthroplastic surgery.