The age and weight of the average person has been increasing over the years, with a higher proportion of the population consisting of the elderly and overweight. Today, about 70% of people over the age of 65 are suffering from osteoarthritis (OA), a disease related both to excess weight and aging. Obesity is a particularly important risk factor for developing OA of the knee.
How Being Overweight Causes Osteoarthritis (OA)
There are two main models that explain how obesity causes OA:
First, obese people carry excess body weight, which places more stress on the body’s joints. This increased force causes the breakdown of cartilage, ultimately resulting in OA. This notion is supported by the fact that knee OA is more strongly related to obesity than hip OA—the knee joint is subjected to more force than the hip joint. Although logical, this concept does not explain why hand OA is associated with obesity, since the hand is not a weight-bearing joint.
The second model is that being overweight may cause the breakdown of cartilage through a systemic factor that reaches all joints, resulting in the development of OA. Unlike the “overload” concept, this model accounts for the relationship between obesity and OA in non-weight-bearing joints, like the hand and neck.
This second model is reinforced by new observations that adipose tissue plays a role not only in storing energy but in secreting certain hormones as well. The level of adiposity affects the endocrine function of the fat tissue. Research shows that the concentration of active substances that circulate in the body is not the same in obese and non-obese people.
A chronic, low-grade inflammation has been observed in obese people, the result of peptides like TNF-alpha and leptin that are produced by adipose cells. These peptides cause inflammatory processes that may contribute to the damage of articular cartilage that is associated with OA.
Can Weight Loss Reduce Symptoms Of OA?
Since obesity appears to cause OA, it is logical to wonder if losing weight can help treat OA’s symptoms. An answer to this question can be found in a review of all the existing studies on weight loss and OA that was published not long ago in the Annals of the Rheumatic Diseases [1].
The review study was conducted in order to determine whether patients suffering from knee OA would experience a lessening of pain and functional disability after losing weight. The results of the meta-analysis found that overweight knee OA patients saw an improvement in levels of physical disability after moderate weight reduction. Specifically, the study recommended that overweight patients reduce their body weight by 5-10%, at a rate of 1.1-3.3 pounds per week, in order to see an improvement in OA symptoms.
Therefore, a weight loss of 1-2 pounds per week, achieved with a safe and clinically studied weight loss program (i.e such as Weight Watchers, Atkins, Nutrisystem, Medifast), combined with appropriate medication and/or supplementation can potentially result in substantial relief from and improvement of OA symptoms.
How Much OA Can Be Prevented By Weight Loss Among The Overweight?
The Framingham OA study [2] found that the risk of developing knee OA would drop 21.4% if either of these two criteria were met:
- Obese men with a BMI>30 reduced their weight to a level that was considered merely overweight (BMI 26-29.9), and
- Overweight men with a BMI>25 reduced their weight to within the normal range (BMI<25).
If men in both categories (overweight and obese) managed to achieve a weight within the normal range, chances of OA would decrease even more.
For women, incidence of knee OA would see a 33% drop if they lost enough weight to move from obese to overweight, and another 33% if they moved from overweight to normal (BMI<25).
In Conclusion
A complete biochemical interpretation of the physiological relationship between obesity, OA, and weight loss is not yet known, but research has shown that excess weight puts people at a greater risk for developing OA in the knees, hips, and hands.
Weight loss is an important component of OA treatment, reducing symptoms like pain and stiffness and increasing joint function. It has been shown that being obese at a young age is related to later development of OA, suggesting that diet programs with a focus on treating obesity are an important preventive measure against OA.
About The Author
Matthew Denos, PhD, is a biology researcher with a keen interest in obesity and its relationship to the development of joint diseases. He follows the current scientific literature on diet and weight loss and reviews weight loss programs on his blog, where he also offers a Nutri system discount code and promo coupons for Medifast, two clinically studied diet programs.
References
- Ann Rheum Dis. 2007 Apr;66(4):433-9. Effect of weight reduction in overweight patients diagnosed with knee osteoarthritis: a review and meta-analysis. Christensen R, et al.
- The epidemiology of knee osteoarthritis: results from the Framingham Osteoarthritis Study. Felson DT. Semin Arthritis Rheum. 1990 Dec;20(3 Suppl 1):42-50.