But you can fight back today - with food.
No time to eat right
Between jobs, boyfriends and maintaining a hectic social life, who has time to eat, let alone eat healthily?
Choose microwave-friendly meals with the perfect balance of protein, carbs and vegies in one package (we like Lean Cuisine Moroccan Lamb with Couscous). In general, look for these qualifications when choosing a frozen feast: 450mg or less of sodium and no more than 3g total fat and 1g saturated fat per 420kJ, says Constance Brown-Riggs, author of Eating Soulfully and Healthfully with Diabetes.
Bonus: Harvard scientists found that every one-serving increase in daily vegie intake decreases your risk of heart disease by four per cent.
A Red Bull can boost your mood temporarily, but it won't improve your long-term outlook.
Eat 1 tbs flaxseeds (aka linseeds) every day. It's the best source of alpha-linolenic acid (ALA), an omega-3 fatty acid that researchers say improves the operation of the cerebral cortex. That's the area of the brain that processes sensory information, including pleasure signals. To meet your quota, sprinkle on salads, vegetables and cereal, mix into smoothies, or dress salads with flaxseed oil.
Whether it's because you're bombing down skateboard ramps or entering too many fun runs, you are seven times as likely to tear a ligament as a man in the same age group
Beef. It's the perfect muscle food because it's packed with protein and creatine - both build muscle, which basically acts like bubble wrap around tendons and joints. Try this ligament-loving Mexican salad recipe: brown 115g extra-lean beef mince over medium heat. As it cooks, sprinkle it with black pepper, 2 tsp chilli powder, and a couple of dashes of Tabasco sauce. Place the cooked beef, 1 diced tomato and 2 tbs reduced-fat cheese over a bed of lettuce and top with salsa.
The bone-building clock is ticking
This is your last chance to strengthen your skeleton. When you hit 30, you're pretty much stuck with what you've got.
Drink two 250ml glasses of vitamin D-fortified low-fat milk every day. You'll get 581mg of calcium and five micrograms of vitamin D, the perfect nutrient combo to develop break-resistant bones. Broccoli also deserves a place on your menu. It contains a respectable 43mg of calcium per cup and is also home to magnesium, vitamin K and phosphorus, all of which, research shows, play a major role in keeping you upright. Find naked broccoli unbearably boring? Top it with a layer of melted reduced-fat cheddar for the ultimate bone-friendly side dish, says dietitian Kerry Neville.