Even though these guys got a lot stronger from lifting weights, their weight and body fat didn’t change much—they just got more muscle without losing fat.

Just because certain muscle traits make someone strong right now doesn’t mean those same traits will help them get stronger from training—what matters for improvement is different.

In young men who lift weights recreationally, eating more than 2.0 grams of protein per kilogram of body weight per day led to slightly greater increases in strength over 8 weeks compared to eating less, even though muscle size increased similarly in both groups. This suggests that strength gains may come from improvements in how the nervous system controls muscles or in lifting technique, rather than just from muscle growth.

In adults with obesity, doing both cardio and strength training for ten weeks leads to a measurable increase in muscle strength, while doing only cardio does not produce the same increase.

When untrained young men lift heavy weights three times a week for five months, they get much stronger—some exercises more than double their original strength.

Over a 10-week period, two different types of resistance training—short, intense sessions and longer, traditional sessions—did not lead to measurable changes in overall muscle mass, fat mass, or body fat percentage in healthy young adults. Small trends suggested the intense training might be slightly better for building muscle and reducing fat, but these trends were not statistically significant.