Sometimes what seems logical in science just doesn't pan out. Take, for example, the idea that if a little bit of a vitamin is good for you, a lot will be even better. That train of logic has received little support from the scientific data. But occasionally, such ideas are valid. A study to be released soon in the journal Arthritis Care and Research is an example of the latter.
It's been a truism that being obese raises the risk of developing arthritis in weight-bearing joints such as the hip, ankle and knee. Thus, the converse would seem to be true that is, if an obese person loses weight, she or he would lower the risk of developing osteoarthritis (the most common kind). This hypothesis was tested by Dr. Jos Runhaar of the Erasmus MC, Department of General Practice, Rotterdam, the Netherlands, and colleagues.
These researchers examined the records of 353 overweight or obese women (BMI ¥ 27 m/kg2), a subset of participants in the PROOF study (Prevention of Knee Osteoarthritis in Overweight Females), which was designed to examine the preventive efficacy of diet and exercise and glucosamine sulphate supplementation on the incidence of knee osteoarthritis. On average, the participants in this subgoup were 56 years old, and had BMIs of 33kgm/m2. They compared the arthritis incidence in women who met a goal of losing either 5 kgm (about 11 pounds) or 5 percent of their body weight within 30 months of beginning the study, to the incidence in women who did not meet that goal. Initially, the women did not suffer from osteoarthritis, as determined by X-ray evidence of joint space narrowing.
The incidence of knee osteoarthritis was 15 percent for women who met that weight loss goal, compared to 20 percent in the women who did not; a numerically small but statistically significant difference. In addition, more of the women who didn't meet the goal had osteophytes (bone spurs along the edges of the joint) than did those who did lose the weight again a statistically significant difference.
This was an observational study, and thus cannot be assumed to reflect a causal relationship, as there may have been confounding factors involved in the results. In addition, the authors pointed out, "Due to the slow progression of the disease, a longer follow-up period will be necessary before the number of prevented cases of knee OA by moderate weight loss becomes clinically more relevant." And it will be important to know if maintenance of weight loss is necessary to continue arthritis prevention it's logical to think so.
So sometimes logic is borne out by science but it still must be tested before we can say with confidence that it's true. As we've said before, the proof of the pudding is in the eating.