20s- Butt-kicking cardio.
Burn major calories with interval training. Your present cardiac fitness level can help predict how healthy you’ll be later.
30s- Targeted toning.
In addition to your regular cardio, fight a slowing metabolism by toning the large muscle groups (chest, back, hamstrings, quads, glutes) three times a week to burn the most fat. Swimming is also a great toning exercise. It is known to improve your mood and you can even try water aerobics for amplified calorie burning and toning.
40s- Weights, weights, weights.
Strength now is crucial for keeping up your metabolism and bone health, so lift at least two to three days a week. Lifting light weights won’t bulk up your muscles, but it will keep them strong.