Low-Cal Diet Plus Exercise May Help Patients With Hip OA

Adding a super low-calorie diet to an exercise program improved some aspects of hip osteoarthritis (OA) in a randomized trial, but maybe not enough to recommend widely.

Outcomes including pain and function as assessed with the Hip Disability and Osteoarthritis Outcome Score (HOOS) instrument, and a global measure of hip improvement, were significantly better after 6 months among patients assigned to the combined approach, according to Michelle Hall, PhD, of the University of Sydney in Australia, and colleagues. Those patients lost substantially more weight than controls randomized to the exercise program alone (mean difference -8.8 kg at 6 months, 95% CI -11.1 to -6.4).

But no difference was seen in a simple patient-reported measure of hip pain severity (mean difference -0.6 on 11-point scale, 95% CI -1.5 to 0.3), which served as the trial’s primary outcome, the researchers reported in Annals of Internal Medicine.

Hall’s group took an optimistic view of the findings. Although the primary endpoint was missed, the diet-plus-exercise program “did benefit most secondary outcomes, including other pain outcomes … suggesting that weight loss may be a potential treatment option for the overall management of hip osteoarthritis.”

In an accompanying editorial, however, two other researchers questioned whether any of the benefits were great enough to matter.

Kristine Godziuk, PhD, of the University of California San Francisco, and Gillian A. Hawker, MD, MSc, of Women’s College Hospital in Toronto, agreed that weight loss ought to be helpful in hip OA. But they questioned the very low-calorie diet approach, which may have led participants to lose the wrong kind of weight.

“Although strengthening exercises were added to the [very low-calorie diet], the diet and exercise group lost approximately 1.5 kg of lean mass in 6 months,” the editorialists pointed out. “As the [study] authors acknowledged, this may have offset the benefits of weight loss, if any, on osteoarthritis-related hip pain.”

Instead, Godziuk and Hawker wondered whether medical weight loss treatments such as GLP-1 receptor agonists might be more effective in helping hip OA patients lose weight while preserving muscle mass, and suggested studies to examine it specifically.

“Only with these data will we be able to comprehensively evaluate and understand potential patient-centered benefits and risks of weight loss in osteoarthritis,” they wrote.

Study Details

Called ECHO, the trial randomized 101 patients in equal numbers to the exercise program either with or without the very low-calorie diet (800 kcal/day) that also kept carbohydrate intake below 50 g/day. Meals were provided to patients assigned to this diet. It was maintained until patients either lost 10% of body weight or had reached week 23, at which point they transitioned over a 2-week period to a “longer-term eating plan” in which patients created more of their own meals and could include more carbohydrates with low glycemic index. When that was completed, patients were encouraged to follow a “healthy diet” patterned after one promulgated by the Australian government. Patients were followed through month 12.

The exercise program included five consultations with a physiotherapist, who provided a set of mainly muscle-strengthening exercises for patients to do at home three times a week for 20-30 minutes per session. The professionals also developed individualized plans to increase physical activity beyond the exercises, and all patients were encouraged to continue with the program on their own after month 6.

Participants were recruited through online ads and from a database of study volunteers at the investigators’ institution. Eligibility criteria included age of 50 or greater, at least 3 months of hip pain rated at least 4 on the 11-point scale, with OA confirmed via imaging, and body mass index (BMI) of at least 27. Those with past hip surgery or had been actively trying to lose weight were excluded.

Mean patient age was 62, and 70% were women. About two-thirds had OA at Kellgren-Lawrence grade 2, the rest were more severe. BMI values averaged about 33 at baseline; mean body weight was about 94 kg (207 lb). Pain at baseline averaged about 5.9 on the 11-point scale, while HOOS scores for pain, physical function, and hip-related quality of life — all on a 100-point scale — averaged about 60, 67, and 46, respectively. All but two participants had data through month 6, and 95 were still participating at month 12.

Generally, these measures improved in both groups, attesting to the efficacy of exercise in relieving hip OA symptoms. The 11-point pain scores reached 3.1 by month 6 in the diet-plus-exercise group, compared with 3.8 with exercise alone. BMI values also fell more in the diet arm (mean difference -3.2 points, 95% CI -4.0 to -2.3). There was some rebound in body weight and BMI after patients went off the very low-calorie diet: by month 12, the between-group difference in weight shrank to -5.4 kg and the BMI difference dropped to -1.9 points, with all still significantly favoring the diet arm.

All three HOOS domains showed significant extra benefit from the diet component at month 6. Pain improved by 18.0 points in the diet arm versus 9.9 points with exercise alone; changes were similar with HOOS function and quality of life. For HOOS pain and function, these differences were also maintained through month 12; improvement in quality of life, however, was no longer significantly superior in the diet arm.

Body composition was evaluated only at baseline and month 6; over that period, the diet intervention was clearly helpful in reducing both visceral fat and total body fat mass, with a mean difference of -402 g and -7,386 g, respectively, relative to exercise alone. But total body lean mass also decreased with the diet program (-1,504 g), which is normally not wanted.

The trial’s chief limitation was that it was not blinded. Others included its Australian sample and the diet and exercise programs’ particulars. “Further research could also consider other dietary interventions, such as the Mediterranean diet with its focus on targeting local and systemic inflammation,” Hall and colleagues observed. Finally, whether the improvements seen with weight loss translated to delayed need for hip replacement surgery wasn’t examined.