Creatine and Muscle: What a 12-Week Trial Found With and Without Exercise

Creatine is best known as a supplement used alongside strength training. A 12-week trial in adults aged 45 to 65 raises a more surprising possibility: participants who stayed sedentary while taking creatine gained lean tissue and improved on strength tests. The result deserves attention, but it doesn’t establish that creatine can replace exercise or that the same changes occur in younger, trained athletes.

What the trial compared

Researchers at Texas A&M University enrolled 73 healthy, sedentary adults in a double-blind, placebo-controlled trial published in the Journal of the International Society of Sports Nutrition. Sixty-four participants completed it: 40 women and 24 men, all between 45 and 65 years old.

Participants first chose whether to take part in a structured exercise and weight-loss programme or continue their usual routines. Researchers then randomly assigned people within each group to take creatine monohydrate or a placebo. Both were taken at a dose of 5 g twice daily, creating four groups: exercise with creatine, exercise with placebo, no exercise with creatine, and no exercise with placebo.

The exercise programme combined resistance and aerobic sessions three times a week with a modest calorie deficit. Researchers assessed body composition using DXA scans at the beginning, at six weeks and at the end of the 12 weeks. They also measured blood markers and cognitive performance.

Changes among sedentary participants

Participants who took creatine without joining the exercise programme gained roughly 1.1 kg of lean tissue over 12 weeks. They also improved their leg press and bench press strength and muscular endurance. Those are notable results for a group that didn’t follow a training plan, but the trial’s size and duration make this an early finding rather than a settled answer about creatine’s effects on people who don’t exercise.

The sedentary creatine group also had favourable changes in some blood lipid measures, a decrease in HbA1c, and higher scores on selected memory and cognitive tests. The researchers describe these results as exploratory. They may point toward questions for future research, but they don’t show that creatine reliably improves blood sugar control, cholesterol or cognition.

Exercise changed the picture further

The clearest practical signal came from combining creatine with exercise and a calorie deficit. Participants who followed the programme and took creatine added nearly 1.4 kg of lean tissue while losing fat mass. Their body fat percentage fell more than it did among participants who exercised and dieted while taking the placebo; that group lost fat but had little change in lean tissue.

Strength improvements also favoured the creatine group. Maximum leg press strength rose by about 34%, compared with 18% for the exercise and placebo group. Bench press strength increased by about 23% with creatine and 12% with placebo. Time to exhaustion improved more in the creatine group as well.

For active people, this distinction matters: the trial points to stronger results when supplementation accompanied a structured programme. It doesn’t show that a scoop alone produces the same changes. The exercise involved both resistance and aerobic work, so these results also can’t identify which element drove each improvement.

Strength effects don’t mean more aerobic capacity

Creatine didn’t improve aerobic capacity beyond the gains associated with exercise. That fits its role in short, hard efforts. Muscles store phosphocreatine, which helps regenerate ATP, a source of energy for muscle contractions. Creatine supplementation can increase those stores, supporting repeated bursts of high effort. That mechanism is more relevant to a short sprint or lifting set than to sustaining a long ride.

Dr. Richard Kreider, the trial’s lead researcher, has studied creatine for more than 30 years. In a 2025 interview with Texas A&M, he said, “Creatine is safe, and it’s important for everybody, not just bodybuilders and athletes.” A 2025 analysis by his team of 685 clinical trials found no significant difference in reported side effects between creatine and placebo. That broad result offers context, while this particular trial still covers only 12 weeks and a specific group of adults.

How to read the results

Some of the apparent increase in lean tissue may reflect water. Creatine draws water into muscle cells, and DXA scans count that water as lean mass. The measured change therefore can’t be treated as a direct measure of newly built muscle.

The group design also limits what can be concluded. Participants chose whether to exercise, so the exercise and sedentary groups weren’t randomly formed. Random assignment applied to creatine or placebo within each group. Differences in motivation or lifestyle between those groups could have influenced the results.

The dose was 10 g per day, above the 3 to 5 g commonly used. The trial doesn’t establish that this higher amount is needed to achieve the reported effects. Kreider noted that obtaining a comparable amount from food would require roughly 2 to 4.5 kg of meat or fish daily; that comparison doesn’t make supplementation necessary for every person.

These findings apply to healthy adults aged 45 to 65 over a 12-week period. They don’t establish long-term effects or predict how younger adults, trained athletes or cyclists will respond. Creatine may be a useful addition to a training and nutrition routine, but the strongest changes in this trial came when it was paired with regular exercise. For riders interested in maintaining strength with age, that’s the practical lead to follow: training remains central, while creatine’s role is still being clarified.