Effects of Two Years of Calorie Restriction on Aerobic Capacity and Muscle Strength: (CALERIE) study

2 years CR title

This article was published in the journal ‘Medicine and Science in Sport and Exercise Science’

Background

Calorie restriction (abbreviated CR) is a popular dietary strategy characterized by a reduction in overall energy intake (classically ~25%) without nutrient deficiency. As such, it is increasingly being studied for its potential benefit on health-span and lifespan. Indeed, CR has been shown in many animal models, including primates, to extend life and health-span. CR effects on primary aging (deterioration in tissue structure and function) and secondary aging (deterioration in tissue structure and function due to adverse lifestyle/environment) are well studied in animal models, but human data is currently lacking. To date, observational studies have been the only mechanism by which CR has been studied – yet they provide evidence that CR may have a variety of health benefits in non-obese humans similar to those observed in animal models. While the cardiovascular benefits of CR show promise, adverse effects of CR also occur; and may include a loss of lean body mass due to skeletal and cardiac muscle catabolism. In addition, a decrease in physical activity with CR in humans has been evidenced, and thus a decrease in muscle mass and muscle activity may lead to paradoxical declines in cardio-respiratory fitness with CR.

What’s new?

The CALERIE study (comprehensive assessment of long-term effects of reducing intake of energy) is the first randomized control trial of caloric restriction in non-obese humans.

What is the purpose of this study?

Caloric restriction has been shown to improve health span and delay the onset of age-related diseases in many animal species. The aim of this investigation is to determine how caloric restriction (CR) may Impact V02 max and muscle strength. This aim is one outcome as part of the larger CALERIE trial.

Participants

218 Healthy, normal weight/mildly overweight men and women (average age 37.9 yrs) completed the study

Methods

The participants were randomized in a 2:1 ratio (CR:AL) into one of two conditions. (1) 25% caloric restriction (CR) or an ad libidum (AL) control diet where no recommendations were given on caloric intake. At baseline, 1 year, and 2 year time-points, participants completed a incremental treadmill test to determine max aerobic capacity (V02 max) and completed a test of leg strength measured with a dynamometer.

Results

Average caloric restriction attained in the CR group was 11.9% during the 2 year intervention (compared to prescribed 25%). In the CR group, body weight decreased by 7.7 kg, whereas no weight change was reported in the AL group (+.2 kg). Absolute V02 max (L/min) decreased in the CR group at year 1 and 2 on the intervention, however, when expressed relative to body weight (ml/kg/min), V02 max increased at both time points (+2.2 ml/kg/min at 1 year, +1.9 ml/kg/min at 2 years). No change in V02 max occurred in the AL control group. In addition to V02 max, treadmill test time and workload increased at 1 and 2 years. Strength changes were observed in the CR group, with a decrease in absolute flexor and extensor strength. However, when expressed relative to body weight, strength was shown to increase. No change in V02 max was observed relative to lean body mass or lean leg mass.

Conclusions

A two year-intervention of modest (~12%) caloric restriction intervention without a prescribed exercise component does not appear to compromise aerobic capacity in non-obese healthy individuals. Future studies should explore the clinical implications of the observed change in V02 mass and muscle strength with CR.

Citation: Med Sci Sports Exerc. 2017 Nov; 49(11): 2240–2249.

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