The metabolism that allowed you to burn through post-drinking trips to the kebab shop in your 20s is now dropping slowly but surely. And even if the number on your scale isn't rising, the number on the tag of your little black dress might well be. In a study published in the American Journal of Clinical Nutrition, people who managed to maintain their weight swapped lean body mass for blubber each decade. Sagging body parts aren't your only hazard. Starting at 30, your systolic blood pressure rises four points per decade and your joints can start acting up. The good news is that this is the decade when you can stiff-arm health ailments that previous generations just accepted as part of getting older.

Here, how to turn back your biological clock.

THE PROBLEM

Corroding joints

Even though arthritis doesn't usually set in until later in life, the damage that causes it is happening now.

THE FIX

Eat three 150g serves of fish per week. Specifically, have salmon, trout or tuna - each serve packs more than 1000mg of omega-3 fatty acids. A UK study found that getting this amount of fish oil daily appeared to reduce cartilage-eating enzymes in a majority of patients facing joint-replacement surgery. Fish oil slows down cartilage degeneration and reduces factors that cause inflammation, says Prof. Bruce Caterson of Cardiff University in Wales, a lead researcher in the study.

THE PROBLEM

Yaaaaawn!

You're climbing the company ladder, maybe getting married and having kids. Dealing with a mother-in-law, a mortgage... You're stretched and stressed to your limits. Oh yeah, and your sex life is about as revved up as a rusty Torana.

THE FIX

Go nuts. Peanuts, hazelnuts and walnuts are loaded with vitamin E, an antioxidant that bolsters the immune system, which gets run down when you're running around. They're also chock-full of B vitamins, which help prepare your body for physical ramifications of stress, like high blood pressure and off-kilter hormones. Nuts are also a great food source of arginine, an amino acid that improves blood flow - to help you get from dead tired to orgasmic. You need only a handful per day, or sprinkle them on yoghurt, salads or muesli.

THE PROBLEM

A slooow metabolism

Your denim shorts fit as if they just came out of the dryer - even though you haven't washed them in weeks and you work out like triathlon champ Emma Snowsill. It's a bitch to stay slim when you're doing all the right things but your metabolism is conspiring to add flab.

THE FIX

Low-sugar, high-protein snacks will keep your metabolic furnace stoked and leave you less likely to binge. Have a slice (42g) of hard cheese - like cheddar, Swiss or provolone - once a day. Cheese has up to 11g protein per serving and almost no sugar, which keeps your blood sugar in check. Other options: a cup of low-fat plain Greek yoghurt or a handful of those magic pills known as almonds.

THE PROBLEM

Cracks in the facade

You're cool with getting older and wiser. What you're not so cool with are the tiny lines starting to show on your face.

THE FIX

Stroll down the bean aisle. A study of 453 elderly people in the Journal of the American College of Nutrition found that those who ate the most legumes and vegies had fewer wrinkles and less sun-related skin damage. Beans are rich in antioxidants that help the body deal with free radicals - skin-damaging molecules caused by sun exposure and pollution. Use hummus as a sambo spread, toss red kidney beans into soups or lentils into pasta sauce, or serve canned beans as a convenient side. Mix them up with face-saving, antioxidant-rich vegies, like asparagus, broccoli, celery, eggplant, onion and spinach (all of which were also found in the study to be the skin's fountains of youth), to make sure you keep getting asked for ID.