Weights alone help little, health-wise, though they might, if you're diet's right, help you look good a little.
Weight lifting alone has significant benefits. It increases bone density - Wolff's law - with obvious benefits for the middle-aged and older. From a young adult standpoint, it's a valuable preventive measure. Anyone can get osteoporosis or break their hips just by standing. Posture can be improved with weigh lifting. People overlook posture, but the body affects the mind. It's easy to feel sluggish or cranky if one has poor posture. The greatest benefits of weight lifting are strength and heart health. Heart rate and blood pressure are affected by one's effort level. If one has strong muscles, the heart doesn't have to work as hard; thus, blood pressure is kept in check. Increased strength can help in even the most mundane tasks. Increased lean mass - a benefit of resistance training - also raises one's metabolic rate.
As for weigh lifting supplementing aerobics, the American Heart Association commented on a study that showed weigh lifting is a good supplement to aerobic exercise. Even without scientific studies provided one is lifting weights around the recommended range of percentage of one's 1 Rep Maximum, I'd guess everyone can attest to their heart rate being elevated.
You gotta work the heart, man. Breaking out into sweat during any exercise regime is a good sign. And keeping fluids (water) in your body helps, too.
There's no better feelings than exercise-induced sweating; it's not only physically healthy, but mentally, too.
If one works out in an air conditioned gym or well-ventilated room, one can be in the lower end of the preferred aerobic heart rate zone of 55% to 85% and not be sweating profusely. (I'm not saying you were calling for excessive sweating, but I'm just talking in general.) I usually do aerobics at around 60% of my maximum heart rate and most days I sweat only a little, but my heart rate is elevated and I still get "runner's high." I've made progress as I've dropped my resting heart rate and am at about 12% body fat from about 22%. It's great, too, because I know I'm getting in shape without feeling exhausted. Now weight lifting is another matter; that's when I sweat. I guess I'm just saying one doesn't have to be sweating bullets in order to have a beneficial aerobic workout.
