Researchers looked at 9 studies involving 408 healthy women to see if taking multi-ingredient protein supplements while exercising could help build muscle and improve body composition. The good news: women who combined protein supplements with exercise gained more muscle mass and strength compared to those who exercised without supplements. However, the supplements didn’t help reduce body fat or improve everyday physical tasks like climbing stairs. The benefits were strongest for older women, those who were overweight, and people who took their supplements right around workout time. This research suggests that protein supplements can be a helpful tool when combined with exercise, but they work best when used strategically.

The Quick Take

  • What they studied: Whether taking multi-ingredient protein supplements (products with protein plus other nutrients) while exercising helps women build muscle and change their body composition
  • Who participated: 408 healthy women ranging from 18 to 73 years old across 9 different research studies. The women were from various backgrounds and fitness levels
  • Key finding: Women who took protein supplements while exercising gained about 0.45 kilograms (1 pound) more muscle mass and showed better muscle growth and strength compared to women who just exercised without supplements. However, supplements didn’t help reduce overall body fat
  • What it means for you: If you’re exercising and want to build muscle, adding a protein supplement may help you see better results—especially if you’re over 40, overweight, or take your supplement close to your workout time. However, don’t expect supplements alone to help you lose fat; they work best for building muscle alongside regular exercise

The Research Details

This was a meta-analysis, which means researchers searched through scientific databases and found 9 high-quality studies that tested whether protein supplements combined with exercise helped women. They looked at studies published through February 2025 that included women doing exercise programs while taking multi-ingredient protein supplements. The researchers then combined all the results from these 9 studies to see what the overall pattern showed.

The studies they included were randomized controlled trials, which is the gold standard in research. This means women were randomly assigned to either take protein supplements while exercising or just exercise without supplements. This random assignment helps make sure the results are fair and not biased.

The researchers used special statistical methods to combine results from all 9 studies, even though the studies had some differences in how they were done. They also looked at whether certain factors—like age, body weight, when supplements were taken, and how long the studies lasted—changed the results.

By combining results from multiple studies, researchers can see the bigger picture instead of relying on just one study. This approach is stronger because it includes more people and different situations. It also helps identify which groups of people benefit most from protein supplements, which is important because not everyone responds the same way to supplements

This meta-analysis included only randomized controlled trials, which are considered the most reliable type of research. The researchers were transparent about their methods and registered their analysis plan before starting. However, the studies included had some differences in how they measured results and how long they lasted, which can affect the overall conclusions. The sample sizes in individual studies were relatively small (ranging from dozens to over 100 women), though combining them gave a larger overall picture

What the Results Show

Women who combined protein supplements with exercise gained an average of 0.45 kilograms (about 1 pound) more muscle mass compared to women who exercised without supplements. This difference was statistically significant, meaning it’s unlikely to have happened by chance.

Muscle growth (called hypertrophy) also improved with supplements and exercise. The effect size was moderate, meaning the improvement was noticeable but not dramatic. Similarly, muscle strength improved more in women taking supplements while exercising compared to those who just exercised.

Interestingly, the benefits weren’t the same for everyone. Older women (over 40) gained more muscle mass when they took supplements with exercise. Women who were overweight also saw bigger gains in muscle mass. When women took their supplements close to their workout time, they gained more muscle. Studies that lasted longer than 12 weeks showed better results than shorter studies.

Younger women showed the biggest improvements in muscle strength, while older women showed the biggest improvements in overall muscle mass. This suggests that age affects how your body responds to supplements and exercise.

The research found that protein supplements combined with exercise did NOT significantly help with reducing body fat, lowering body fat percentage, reducing waist circumference, or improving functional performance (like how well someone can do everyday activities). This is an important finding because many people take supplements hoping to lose fat, but this research suggests that’s not where supplements help most. The supplements appear to work specifically for building muscle, not for fat loss

Previous research has shown that protein is important for building muscle when combined with exercise. This meta-analysis confirms that finding and adds important details about which groups benefit most. It also clarifies that while protein supplements help build muscle, they don’t automatically lead to fat loss—a common misconception. The finding that timing matters (taking supplements near workout time helps more) aligns with what exercise scientists have theorized about how muscles use protein

The studies included had different designs and measured things slightly differently, which can make combining results tricky. Some studies were shorter than others, and the number of women in each study varied. The research only included healthy women, so results might not apply to women with health conditions. Most studies didn’t control for total calorie intake carefully, which matters because building muscle requires adequate overall nutrition. The research is limited to multi-ingredient supplements, so results might not apply to simple protein powders. Finally, most participants were relatively young to middle-aged, so results for very elderly women are less certain

The Bottom Line

If you exercise regularly and want to build muscle, adding a multi-ingredient protein supplement may help you see better results (moderate confidence). Take your supplement close to your workout time for best results. If your main goal is losing fat, supplements alone won’t help—focus on overall diet and exercise instead (high confidence). For best results, commit to at least 12 weeks of consistent exercise and supplementation (moderate confidence)

Women who exercise regularly and want to build muscle should consider this research. It’s especially relevant for women over 40, women who are overweight, and anyone looking to improve muscle strength and size. Women whose main goal is fat loss should know that supplements won’t directly help with that goal. People with certain health conditions should talk to their doctor before starting supplements

Most studies lasted 8 to 24 weeks, with better results in studies lasting longer than 12 weeks. You should expect to see noticeable muscle improvements within 8-12 weeks if you combine supplements with consistent exercise. However, changes in body fat take longer and may require 16+ weeks of consistent effort

Want to Apply This Research?

  • Track weekly muscle strength by recording the weight used and number of repetitions for 2-3 key exercises (like squats or chest press). Also measure arm circumference or take progress photos monthly to monitor muscle growth visually
  • Set a reminder to take your protein supplement within 30-60 minutes after your workout sessions. Log each supplement intake in the app alongside your exercise to build the habit of pairing them together
  • Create a monthly check-in where you record body measurements (arm, thigh, chest), take progress photos, and note any changes in how your clothes fit. Track exercise performance metrics weekly to see strength improvements over time. Set a 12-week goal to allow enough time to see meaningful results

This research summary is for educational purposes only and should not replace professional medical advice. Before starting any new supplement regimen, consult with your healthcare provider or registered dietitian, especially if you have underlying health conditions, take medications, are pregnant or breastfeeding, or have allergies. Individual results vary, and supplements work best when combined with consistent exercise and a balanced diet. This meta-analysis included only healthy women, so results may not apply to everyone. Always choose supplements from reputable manufacturers and discuss your fitness and nutrition goals with qualified professionals