@JLeslie Yoga involves muscle contractions. Muscles that repetitively contract get stronger over time. That means people doing yoga should gradually be able to hold poses for longer and do more difficult poses that they were once unable to do. There’s also a good bit of core work involved in yoga, so sure, they probably can do more sit-ups than the average person. However, the thing about body weight exercises is that it only allows you to do more reps of the same body weight exercise. Doing the 30-day squat challenge where you eventually get up to 1000 squats in a day or something stupid like that – all it’s going to do is make you better at body weight squats. No amount of body weight squats is going to allow you to build the strength necessary to squat a barbell as heavy as you are. So, saying that yoga builds strength over time is true, but it’s important to realize that the amount of strength you build isn’t really all that much in the grand scheme of things. And that’s fine, if you don’t care about being strong enough to lift a lot of weight.
Doing yoga while losing weight also will not prevent muscle loss in the way lifting heavy will. As long as you’re eating at a deficit and losing weight, you’re losing both fat and muscle. In order to prevent that loss, you need to do strength training with weights that are heavy (to you), which yoga does not allow you to do.
@FireMadeFlesh Muscular endurance is a whole other thing. The OP didn’t say (s)he is looking to build muscular endurance, and not everyone is. I couldn’t care less about muscular endurance, personally. It would depend on the goals of the individual, but if we’re talking losing fat, gaining strength, and looking good, high weight/low reps will get the job done faster than low weight/high reps. Newbie gains when lifting heavy are way better than newbie gains with low weight/high reps. If the person is looking to run a marathon, they’re probably not going to do much power lifting. If the person just wants to be healthy, strong, and hot, then the heavier that barbell the better.
I’m a member of a huge fitness site, and I constantly talk to women that have been lifting those little 10 lb dumbbells at high reps and calling it weight lifting for months or years and are really unhappy with the results. They don’t feel stronger and they can’t see much of a difference in their bodies. Once they put those baby weights down and start using heavy weights, they’re amazed by the changes in their bodies. I haven’t seen one women try lifting heavy and then go back to light weights.
I agree that results are better when you focus on good nutrition (aka a healthy balance of carbs, protein, and fats), but the fact remains that muscles need calories to grow – if a dude lifts heavy but eats at maintenance, he’s never going to get big and muscular. He’ll build strength, lose a bit of fat, gain a bit of muscle, and get that lean/athletic appearance, but he’d need to eat at a caloric surplus in order to bulk. The same applies to women, only the bulking is WAY harder to accomplish.
If we’re talking weight loss, though, it’s calories in vs. calories out. If I eat 2000 calories of super “healthy” foods, I’ll maintain my weight. If I eat 2000 calories of chocolate, I’ll still maintain my weight. With lifting, yes, it’s definitely a good idea to have a healthy balance of carbs, protein, and fat, but that’s not because it helps with weight loss; it’s because it helps with your results at the gym (energy and strength gains, for instance). And, contrary to what you said in your first response, eating less carbs and protein while lifting light weights when you’re looking for a lean/athletic build isn’t going to do you any favors.