A 12-week randomized, placebo-controlled trial published in the Journal of the International Society of Sports Nutrition enrolled 64 healthy adults aged 45–65 who were not meeting physical activity recommendations. The study population was middle-aged rather than elderly; participant baseline inactivity was an inclusion context noted by the investigators because muscle loss accelerates with age. Testing included DXA-derived body composition, strength measures, blood markers, and cognitive assessments conducted at baseline, 6 weeks, and 12 weeks.
Participants chose whether to take part in a supervised training program that consisted of three sessions per week; 38 opted into the exercise intervention and 26 remained sedentary for the trial. On non-training days, all participants were asked to walk 10,000 steps. Within each activity group, participants were randomly assigned to receive either creatine supplementation or a matched placebo twice daily in a double-blind fashion.
Diet was standardized using an American Heart Association–guided macronutrient distribution: 55% carbohydrate, 15% protein, and 30% fat. The feeding plan was also designed to induce a daily calorie deficit of approximately 300–500 kcal. Compliance with diet and exercise guidelines was tracked but reported adherence was noted by the authors as a potential limitation.
The primary body-composition finding was that participants taking creatine who did not participate in the supervised exercise program gained about 2.4 pounds of lean tissue over the 12-week period. These sedentary creatine recipients also achieved greater bench-press and leg-press strength at 12 weeks compared with their placebo counterparts.
Participants who combined the supervised training program with creatine supplementation gained slightly more lean tissue—about 3 pounds—and demonstrated greater strength improvements and a longer time to exhaustion, an indicator of high-intensity exercise capacity. In contrast, those in the exercise intervention who received placebo showed little change in lean tissue by 12 weeks, suggesting an additive effect of creatine on training-related adaptations in this cohort.
The authors highlighted that these gains occurred despite the relatively modest protein content of the diet (15% of calories). They suggested future research should evaluate whether higher protein intake alongside creatine would further modify outcomes, particularly among sedentary individuals.
Beyond changes in body composition and strength, the study observed favorable changes in certain blood lipids, measures of glucose control, and in cognitive function among participants taking creatine in both exercise and sedentary groups. The trial authors characterized these metabolic and cognitive outcomes as exploratory and recommended additional research to confirm and clarify these signals.
Several limitations were reported or noted by independent experts in the article:
Participants self-selected into the exercise arm rather than being fully randomized to activity condition, which could introduce selection bias if those who chose to exercise were more health-motivated.
Adherence to the prescribed dietary pattern and exercise prescriptions varied and may have affected results; the study relied on participant compliance to the AHA-style diet and step goals.
The sample size was relatively small (64 participants) and the cohort was middle-aged (45–65), so findings may not extend to older adults.
Lean tissue was measured by DXA, which assesses lean mass but does not directly measure muscle tissue or muscle fiber changes.
The metabolic and cognitive findings were described as exploratory and require replication in larger, more controlled trials.
Study lead author Richard Kreider, PhD, proposed a potential mechanism for gains in sedentary participants: creatine monohydrate increases muscle energy availability, which may make daily activities feel easier and thus increase non-exercise physical activity and functional movement. External experts emphasized caution and context.
Şebnem Ünlüişler, MSc, noted the study adds evidence that creatine could be part of a healthy aging strategy because lean mass improvements were seen without structured exercise, but she stressed that resistance exercise, adequate protein intake, and good metabolic health remain primary priorities.
Clarinda Hougen, MD, a sports-medicine clinician, agreed that creatine can be a useful adjunct to resistance training and proper nutrition. She reiterated that creatine does not directly burn fat but, when combined with training, can increase fat-free mass, strength, and potentially improve insulin sensitivity and metabolic profile over time.
This 12-week study in adults aged 45–65 found that twice-daily creatine supplementation was associated with gains in lean tissue and strength even in participants who did not take part in a structured exercise program (about 2.4 lb), with larger gains when creatine was combined with supervised training (about 3 lb). The trial also reported exploratory improvements in some blood lipids, glucose control, and cognitive function. Limitations include self-selection into the exercise arm, adherence variability, small sample size, and reliance on DXA to measure lean tissue. Authors and external experts framed creatine as a potential adjunct for preserving muscle and supporting metabolic health in middle age, not a replacement for resistance exercise and adequate protein intake. Further controlled research is needed to confirm metabolic and cognitive effects and to test combinations with higher protein intake or in older populations.