Weighing the Effects of Obesity on Feet, Ankles, Knees, Hips, and Testosterone Levels
According to the American Obesity Association, 66.3% of adult Americans (about 200 million) are overweight or obese. Gert Bronfort, DC, director of research at Northwestern Health Sciences University, says, “There’s no question that obesity is a major health problem in the United States. Costs attributed to obesity-related diseases approach $100 billion annually.”
Not only is obesity well documented and well publicized as leading to life-threatening conditions such as cardiovascular disease and diabetes; it can also stress joints and degrade cartilage in the lower half of the body, ultimately resulting in joint problems and osteoarthritis (OA).
“Cartilage in the knees and ankles also functions like a shock absorber,” comments James DeVocht, DC, associate professor at Palmer College of Chiropractic. “As joints deteriorate from the constant stress of too much weight, the gradual loss of cartilage results in more shock waves and jarring throughout the body.” A recent study by Teichtahl et al.1 confirms a direct relationship between increased levels of obesity and adiposity and increased annual patella cartilage volume loss.
Other complications from obesity include inflammation, chronic pain, and depression, all of which can complicate treatment plans. The obvious goal for treating obesity is weight reduction through exercise and healthier eating habits. Manual therapy during these lifestyle changes is essential for counteracting stress on joints in the lower body, as well as reducing pain—both of which help keep patients on the road to recovery.
“Medication without mechanical treatment, or without increase in activity level, is largely an ineffective approach,” says Jay Greenstein, DC, a chiropractor in Fort Washington, Md. “Obese patients must be involved in their own care and get themselves up and moving—and DCs are in a perfect position to assist this patient population.”
Obesity and Osteoarthritis
More than 60 years of research have revealed a strong association between obesity and osteoarthritis, especially in weight-bearing joints. “Numerous cross-sectional and longitudinal epidemiological studies have shown that body mass index (BMI) correlates significantly to the incident risk of radiological and symptomatic knee osteoarthritis,” states Francis Berenbaum, professor of rheumatology at Saint-Antoine Hospital in France.2 “By destroying cartilage and ligaments in the weight-bearing joints, the increased mechanical load related to obesity increases the risk of osteoarthritis. Repeated overloading of a normal joint can also induce abnormalities in the extracellular matrix, as well as chondrocyte and osteoblast behavior.”
A number of studies have concluded that obesity is a major risk factor for knee OA and associated functional impairment. Coggon et al.3 determined that the risk for knee OA in people with a body mass index of 30 kg/m2 or greater was 6.8 times that of normal-weight controls.Another study4 demonstrated that people with a BMI greater than 30 kg/m2 were 4.2 times more likely to have knee OA, and both studies linked knee OA and obesity with impaired physical motion.
Although a clear association exists between obesity and knee OA, the connection between obesity and other musculoskeletal disorders such as hip OA is inconsistent.5-7 “For example, the relationship between obesity and hip osteoarthritis, if it exists, is substantially weaker than that of knee osteoarthritis,” comments Dr. Bronfort. “Interestingly, an association between obesity and hand osteoarthritis8 may also exist, suggesting a common unknown factor unrelated to mechanical loading may explain the relationship between obesity and osteoarthritis.”
Impaired Function and Gait
Excess weight is a major factor in restricting normal movement of the body. “How far forward or backward a person can lean and still maintain balance is greatly reduced for obese individuals,” says Dr. DeVocht. For example, static and dynamic stability tests were performed by W.B. Janusz to clarify the impact of excessive body weight on postural control.9 Significant reduction in postural sway was observed in all patients with increased body weight, which limited their dynamic stability range.
Because obese people are more unstable when they stand or walk, they tend to alter their gait to stabilize their larger mass and reduce the risk of falling. To lighten the load on their knees, they take shorter steps that reduce knee extensor torque—the greater the BMI, the shorter the stride and the lower the knee-joint extensor/flexor torque. A shift from overall extensor torque to a dominant flexor torque may occur in highly obese people, resulting in the hamstrings providing knee stability, instead of the quadriceps.10
Research conducted by Stephen Messier, a professor atWake Forest University, discovered that obese subjects also walk with bilaterally abducted forefeet—a stance that was 276% more toed out, compared with normal-weight people.11 Severely obese people also presented more rearfoot motion, including greater touchdown angle, more pronation range of motion, and faster pronation—making them more susceptible to injury, discomfort, and decreased mobility.
A strong connection exists between obesity and pain, including aching joints, lower-back pain, and neuromuscular pain such as fibromyalgia. Chronic pain is debilitating and depressing. Because its causes are often complex, it’s also difficult to treat.
In a recent Journal of Pain study,Okifuji et al.12 studied the relationship between obesity and fibromyalgia syndrome (FMS). A total of 215 FMS patients completed detailed questionnaires about their FMS-related symptoms and underwent tender-point examinations, physical-performance tests, and seven-day home sleep assessments. Forty-seven percent of the subjects were obese, and 30 percent were overweight. Results showed that obesity was linked to greater pain sensitivity, especially in the lower body areas, reduced physical strength and lower-body flexibility, and shorter sleep duration. Several recent studies support the connection between obesity and low-back pain. “Shiri showed that one of the greatest predictors of low-back pain in young Finns is abdominal circumference,” states Dr. Greenstein. After examining data on more than 60,000 subjects,Heuch13 reported a correlation between high BMI and low-back pain in both men and women. “This large population-based study indicates obesity is associated with a high prevalence of low-back pain,” he writes.
Another painful condition related to obesity is plantar fasciitis and heel pain. The additional pressure from excess weight on the medial longitudinal arch may be harmful to the plantar ligaments, causing them to collapse. A case-controlled study revealed that obese subjects were five times as likely to have heel pain as their normal-weight counterparts.14
Obesity contributes to inflammation, especially in the joints. “Excess weight irritates the joint surfaces, causing stress and inflammation,” says Dr. DeVocht. “Increased inflammation also makes the body more susceptible to other health problems.” Inflammatory response is especially related to adipose tissue, which secretes compounds known as cytokines, cell-to-cell signaling proteins that are linked to excessive weight gain, increased inflammation, and chronic diseases such as knee OA.15 Nutrient excess and insulin resistance are also both related to this excessive pro-inflammatory cytokine response.16
“Nutrient excess produces reactive oxygen species, resulting in oxidative stress that damages cells and triggers an inflammatory response,” explains Messier.17 “The increased inflammation blocks the protective action of insulin, which normally stimulates target cells to take up nutrients.”
However, as excessive nutrients are consumed, neighboring cells and tissues that remain insulin-sensitive are at higher risk. As insulin resistance progresses, inflammation gets worse, initiating a cycle of excessive nutrient intake/insulin resistance/inflammation.18
Intervention and Treatment
Reducing and maintaining body weight is essential for controlling OA pathogenesis. Weight loss reduces risk factors for knee OA and lowers the level of inflammation that is believed to be a factor in cartilage degradation.Weight loss is also associated with decreased pain and improved function, most notably when combined with physical exercise.19
Interventions designed to promote dietary weight loss and exercise in obese people with OA have demonstrated clinically significant improvements in symptoms and disease risk factors.“Both longitudinal cohort studies and randomized controlled trials20-21 show that weight reduction by diet alone or diet and exercise can improve function associated with knee osteoarthritis,” says Dr. Bronfort. Felson22 also showed that a 5.1-kg loss in body mass over a 10-year period reduced the odds of developing OA by more than 50%.
Although it’s natural for patients with OA to want to avoid physical activity, exercise is an effective treatment. Studies have shown that pain, physical function, and walking distance improved anywhere from 15% to 31% with short-term exercise.23-24 Long-term walking and resistance training programs have resulted in self-reported improvements in function up to 11%, slowing the decline in physical function commonly seen among OA sufferers.25-27
That said, exercise and weight loss may not help all arthritic conditions. “There is a lack of evidence regarding the effectiveness of weight reduction for the treatment of other musculoskeletal disorders, like hip osteoarthritis and low-back pain,” cautions Dr. Bronfort. “Despite this, most guidelines21,28 recommend weight loss as a treatment for osteoarthritis because the widespread benefits of weight reduction for obese patients outweigh the risks.”
Exercise and weight-loss programs can seem daunting to obese individuals, with goals that appear impossible to reach. Factors that help achieve long-term success are behavioral-change strategies, extended treatment, increased hours of intervention contact, adherence to rigorous diet exercise plans, and having the support of friends and family.
“Individual attention to coping strategies and increased intervention efforts during the maintenance phase have produced success,” writes Messier.16 “Approximately 80% of clients on moderate calorie restriction remain in treatment for 20 weeks, and approximately 50% lose 9.1 kg or more.”
Personal contact and systematic follow-up are vital components to successful, long-term dietary weight loss. Research29 has shown that participants in a 20-week behavioral therapy program, followed by an 18-week maintenance program with biweekly contact, maintained a 13-kg weight loss. Another study30 reported a 14.7% loss over two years for women following a moderate energy-restricted diet of 1,300 kcal/d for the first year and 1,500 kcal/d for the second year. Other tools used to achieve these results were education, goal-setting, self-monitoring, and creating a structured exercise program.
“People are more likely to try a behavior if the perceived consequences have a favorable cost/benefit ratio,” continues Messier.16 “Some people simply do not know the negative health effects of being overweight/obese and sedentary, or are unduly optimistic about their own fate. They often become discouraged when lifestyle interventions 1) do not meet their unrealistic expectations about how much weight they can lose, 2) cause pain and fatigue, or 3) prohibit a valued food.”
Because obese patients are often in pain, Dr. Greenstein suggests completing a fear-avoidance questionnaire to determine how high their pain avoidance behaviors may be. “It’s essential to sit down and discuss their situation with them,” he says. “When talking with patients about exercise, find out what they like to do and don’t like to do. Try to design an effective exercise routine that interests them personally.”
Dr. Greenstein also suggests conducting a functional-movement screen before designing a treatment program. “These seven standard tests can quickly evaluate the quality of movement patterns and identify any potential biomechanical problems,” he says. “Above all, stay up to date on their progress and keep in touch with frequent communication, especially as they ease into the after-care component of the program.”
Obesity and Testosterone Levels Linked
Obesity has now been linked to another health problem that affects men only—low testosterone levels.
In a recent study31 at the University at Buffalo, endocrinologists revealed that 40% of obese participants had lower-than-normal testosterone readings. That number rose to 50% among obese men with diabetes. The conclusion? As BMI rises, testosterone levels fall.
“These observations have profound pathophysiological, clinical, epidemiological, and public health implications,” says Sandeep Dhindsa, MD, an endocrinology specialist and first author on the study.
“This is just another good reason to stay lean and get fit,” adds David Radford, DC, owner of the Chiropractic Clinic of Solon in Solon, Ohio. “Testosterone, as well as estrogen, get diluted in adipose tissue and are not easy to replete.”
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