Excess weight is a well-established risk factor for osteoarthritis (OA). The Arthritis, Diet, and Activity Promotion Trial (ADAPT) demonstrated for the first time that exercise that is combined with calorie restriction, designed to reduce body mass index (BMI), could also improve physical function and reduce knee pain [Messier SP et al. Arthritis Rheum 2004]. The trial, however, did not demonstrate any effect of diet and exercise on OA progression.

The same authors embarked on a long-term study to test the hypothesis that intensive weight loss (at least 10% of total body weight), along with exercise, would significantly impact the mechanical and inflammatory pathways of OA. Stephen P. Messier, PhD, Wake Forest University, Winston-Salem, North Carolina, USA, and colleagues launched the Intensive Diet and Exercise for Arthritis [IDEA; NCT00979043] trial, an 18-month study that was designed to evaluate the impact of intensive weight loss, with or without exercise, on disease progression.

A primarily Caucasian, female patient population (n=454) with radiographic knee OA and a mean age of 65 years and body mass index (BMI) of 33.6 kg/m² were randomized to one of three arms: (1) intensive dietary restriction alone; (2) intensive dietary restriction plus exercise; or (3) exercise alone. An intention-to-treat analysis was used to compare changes in pain, function, and mobility between groups at 18 months of follow-up.

Eighty-eight percent of patients completed the study. Eighty-five percent of participants had bilateral knee OA. Mean weight loss was 9.5 kg (9.5%) in the dietary restriction-only group, 10.6 kg (11.4%) in the dietary restriction-plus-exercise group, and 2.0 kg (2.2%) in the exercise-only group. None of the participants regressed to her baseline weight during follow-up.

At 18 months, all subjects experienced a decrease in Western Ontario and McMaster University Osteoarthritis (WOMAC) pain scores from baseline. Pain was significantly lower in the dietary restriction-plus-exercise group (51% lower than baseline pain), compared with the 27% reduction in the dietary restriction-only group and 29% reduction in the exercise-only group (p<0.0004). The dietary restriction-plus-exercise group also significantly improved (p=0.003) on the WOMAC function scale (47% relative to the 30% improvement in the dietary restriction-only group and 24% in the exercise-only group).

All groups demonstrated improvements in walking speed, a measure of mobility. However, walking speed was significantly faster in the dietary restriction-plus-exercise group (p<0.004) than either the dietary restriction- or exercise-only group.

“Generally, there is a 1% to 2% decrease in walking speed per decade up to age 62,” said Dr. Messier. “When a 12% to 16% decline occurs, it is unexpected.” In contrast, the intensive dietary restriction-plus-exercise cohort increased their walking speed by 12%, for a walking speed that was faster than that of healthy women aged 40 to 62 years and equivalent to that of healthy middle-aged men. The study cohort reversed the trend of declining mobility that is seen in older adults. Pain can be significantly reduced and mobility and function improved with long-term, intensive dietary restriction and moderate exercise.