Rheumatoid Arthritis Reduces Physical Activity

Source: Tufts University
December 20, 2002 (Reviewed: December 16, 2004)

Among the metabolic changes often seen in rheumatoid arthritis (RA) is an increase in resting energy expenditure, particularly in those patients whose disease is not well controlled. Clinicians might be prompted to encourage increased caloric intake to compensate for this wasted energy, but a study in the American Journal of Clinical Nutrition asks them to rethink this strategy, based on the observation that those with RA expend less energy in physical activity.

Tracking energy balance

Tufts University researchers recruited 40 women - 20 with mild to moderate rheumatoid arthritis and 20 healthy controls matched for age and body mass index. After measurements of resting energy expenditure and body composition were made, each woman consumed a dose of doubly labeled water. They were instructed to collect a daily morning urine sample for the following 14 days, to complete a 4-day food intake record, and to wear a physical activity monitor during waking hours.

At the end of the 14-day collection period, resting energy expenditure (REE) was measured by means of indirect calorimetry, and total energy expenditure (TEE) through the use of doubly labeled water. The thermal effect of food (TEF) - the calories spent digesting and absorbing food - was estimated as 10% of TEE. These measurements were used to calculate the energy expended in physical activity (EEPA).

Differences in energy expenditure

In this study, there was no difference in REE between the two groups (although this value is often elevated in people with RA), nor was there a statistically significant difference in energy intake. There was a difference, though, in how energy was expended. TEE in the women with RA was 1344 kJ/day (320 kcal) lower that that of the controls. This variance was largely due to 27% lower mean energy expenditure from physical activity - the women with RA took substantially less daily exercise than did the women in the control group.

Disease management

People with RA commonly develop 'rheumatoid cachexia,' characterized by lower-than-normal body cell mass, elevated resting energy expenditure, and elevated whole-body protein catabolism. This trio of symptoms leads to reduced muscle strength and increased fat mass, both of which contribute to adverse health effects. According to the authors, medications can keep inflammation under control, but do little to limit cachexia development.

Compounding the problem, say the authors, is that a pattern of inactivity, similar to the one seen in the RA patients in this current study, could contribute to unhealthy levels of body fat. Increasing caloric intake is, therefore, not the answer. The authors say that, when it comes to RA therapy, even the latest generation of anti-rheumatic drugs is not enough. Attention to diet and exercise - especially strength training - should be a key part of disease management.

Source

• Low physical activity reduces total energy expenditure in women with rheumatoid arthritis. R. Roubenoff, J. Walsmith, N. Lundgren,  et al., Amer J Clin Nutr, 2002, vol. 76, pp. 774--779

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