When training for a better body, a huge time waster for the average person is to train each muscle separately. Your muscles will get bigger faster by training multi-joint lifts such as squats, deadlifts and bench press because you can use heavier weights.
This allows you to overload the muscle to a greater degree, which means you’re applying a larger stimulus to the muscle, telling it to adapt and grow.
Favoring the “big” lifts allows you to create a lot of metabolic stress so that your body produces hormones that are involved in tissue repair. Growth hormone, testosterone (for men), and other hormones are released in response to workouts that recruit a lot of muscle.
Furthermore, most of the big lifts work the whole body in a way that is useful for real life, whether it be sports, doing heavy hard work, or just the ability to move with speed and grace.
Bottom Line: Ideally, you should train four times a week using training splits (two days upper body and two days lower) to maximize recovery.
However, if you’re not consistently able to devote one hour, four days a week to training, you should do total body workouts rather than body part splits. This will maximize your time by training the greatest amount of muscle in the least time