Resistance training and dietary protein may help improve body composition, oral glucose tolerance and skeletal muscle content in older persons, a new study suggests.
Researchers from Purdue University in West Lafayette, Indiana and the University of Missouri & Harry S Truman VA Hospital in Columbia, Missouri explained that resistance training (RT) and dietary protein independently influence indexes of whole-body glucose control, though their synergistic effects have not yet been documented.
The study investigated the influence of dietary protein intake on RT-induced changes in systemic glucose tolerance and the contents of skeletal muscle insulin signaling proteins in healthy older persons.
The study included 36 older men and women (age 61 years and older). Participants performed RT (three times/week for 12 weeks) and consumed either 0.9 grams protein · kg-1 · d-1 [lower-protein (LP) group; ~112 percent of the recommended dietary allowance (RDA)] or 1.2 grams protein · kg-1 · d-1 [higher-protein (HP) group; ~150 percent of the RDA]; the HP group consumed more total, egg and dairy proteins.
Researchers found that after RT, body weight was unchanged. However, whole-body protein and water masses increased and fat mass decreased with no significantly different responses observed between the LP and HP groups. The RT-induced improvement in oral glucose tolerance (decreased area under the curve, AUC) was not significantly different between the groups (LP: -28 percent; HP: -25 percent).
The insulin (-21 percent) and C-peptide (-14 percent) AUCs decreased in the LP group but did not change significantly in the HP group. Skeletal muscle insulin receptor, insulin receptor substrate-1 and Akt contents were unchanged, and the amount of atypical protein kinase C, a protein involved with insulin signaling, increased 56 percent with RT, independent of protein intake.
Researchers concluded that older persons who consume adequate or moderately high amounts of dietary protein can use RT to improve body composition, oral glucose tolerance, and skeletal muscle aPKC content without a change in body weight.