Sustained caloric restriction reduces more fat than muscle, organ tissue

Calorie restriction (CR) for 2 years in young individuals without obesity significantly impacts body composition, including a preferential loss of adipose tissue, such as visceral fat, over muscle and organ tissue, a recent study has shown.

A team of investigators used whole-body magnetic resonance imaging (MRI) to evaluate the effect of 2-year CR on changes in body composition.

Forty-three healthy adults (aged 25–50 years, body mass index 22–28 kg/m²) from an ancillary study of the Comprehensive Assessment of Long-term Effects of Reducing Intake of Energy (CALERIE) trial were randomized to 25-percent CR (n=28) or ad libitum (AL) eating (n=15).

Participants underwent whole-body MRI at baseline and at month 24 to measure adipose tissue in subcutaneous (SAT), visceral (VAT), and intermuscular depots (IMAT); skeletal muscle; and organs including brain, liver, spleen, and kidneys, but not heart.

Individuals in the CR group lost more adipose tissue and lean tissue than those in the control group (p<0.05). At baseline, total tissue volume in the CR group consisted of 32.1 percent of SAT, 1.9 percent of VAT, and 1.0 percent of IMAT; the loss of total tissue volume over 24 months covered 68.4 percent, 7.4 percent, and 2.2 percent of SAT, VAT, and IMAT, respectively, which indicated a preferential loss of fat compared with lean tissue.

More muscle loss was noted in CR than AL (p<0.05), but the loss of muscle over 24 months in the CR group consisted only 17.2 percent of the loss of total tissue volume. Changes in organ volumes did not differ between CR and AL.

Moreover, the degree of CR (% decrease in energy intake vs baseline) had a substantial effect (p<0.05) on changes in VAT, IMAT, muscle, and liver volume (standardized regression coefficient ± standard error of estimates: 0.43±0.15 L, 0.40±0.19 L, 0.55±0.17 L, and 0.45±0.18 L, respectively).

“Sustained CR promises to extend the lifespan,” the investigators noted.