Muscle v fat
These two hate each other, but there should be no mistaking whose side you are on.
Muscle is the the key to good health: it burns off fat to use as energy, so the more you have on your body, the more calories you burn even when you're not exercising. Muscle tissue also raises your body's metabolic rate and increases testosterone levels, which boost sex drive and fight premature ageing. Muscle growth also leads to better cardiovascular health, less back pain and has even been linked to improved mental health.
But without your help, it won't stick around for long. To help muscle defeat its fatty nemesis, you need to exercise regularly and eat well. Balance cardio workouts such as running and cycling with resistance training to tone and build lean muscle. You should also try and make space in your weekly fitness programme for high intensity interval training, which will send your metabolism into hyperdrive.
Your diet should be full of fresh fruit and vegetables, low on booze and favour protein over carbs. Finally, remember that not all fats are created equal, and some are even good for you. Replace saturated fats (found in biscuits, cakes, crisps and other junk) with smaller amounts of monounsaturated fats in nuts, fish and olive oil.