New ways to fitness Junk those old beliefs and rev up your health with these new fundas on exercise and diet   Sit-Ups are a waste of time! Old diet rule: Do Sit-Ups New diet rule: Do Push-Ups A recent study, by Youngstown State University in Ohio, has found that sit-ups are a waste of time. Sit-ups alone won't flatten your stomach. In fact, when you do hundreds of sit-ups or crunches, your abdominal muscles can overdevelop and you can get a pot belly. A better exercise for keeping your stomach flat is a push-up. It works your abdominals, arms, legs and back .  Don't Fret about calories Old diet rule: Count calories New diet rule: Count carbs and protein Ditch calorie counting in favour of calculating the protein, carbohydrate, fibre and fat content of food. For example, a marshmallow has zero fat in it, but it's packed with sugar which converts to fat once you've eaten it plus sugary food causes your body to store fat and disrupts your blood sugar levels, which leads to increased hunger. An avocado has a high fat content, but it's the heart-healthy type (polyunsaturated) and is also full of essential fatty acids. These help your body burn fat, especially around your waist and stomach. You should balance each meal so it contains a good mixture of protein, carbs, fibre and fat. For example, go for a chicken and avocado salad - there's protein in the chicken, good fat in the avocado, and fibre and carbs in the salad and vegetables. Don't eat an all-carb meal such as a bowl of pasta - the sugar in the carbs will just convert straight to fat in your body.    Get shot of sugar Old diet rule: Low fat New diet rule: Low sugar Once upon a time, low fat was the ultimate diet mantra. But now it's low sugar. Sugar was used as a treat or in small quantities and was never a problem. But today, over a third of the calories we consume come from sugar or white flour, which is highly refined and acts just like sugar in our system. Fat isn't the problem sugar is. Sugar is just about the worst thing we can have in our diets, because it quickly converts to fat in the body, encourages it to store fat around our middles, makes us more tired, causes wrinkles and leaches vitamins from our body. Cut out the more obviously sugary foods like biscuits, cakes and sweets. Also, avoid less obvious sugar traps such as white carbs (bread, pasta etc), alcohol and foods marketed as 'low fat', as these are often packed with sugar.    Don't sweat it Old diet rule: Sweat it New diet rule: Relax If you want to lose weight, step off the treadmill and take it a bit easier instead. Recent studies have shown that cutting back on cardio (any exercise that makes you sweaty, such as running, tennis, cycling) and lifting hand-held weights or doing yoga will help you burn more calories. Doing too much cardio can actually slow down your weight loss. That's because it stresses out your whole body. When we're stressed, our bodies become flooded with the stress hormone cortisol that encourages fat storage. Cut back on the cardio and do a relaxing exercise class instead, such as yoga or Pilates. This helps reduce stress in the system, which revs up your body's ability to burn fat. Massage has the same effect it encourages your body to burn fat. Fat isn't the problem sugar is. It quickly converts to fat, makes us tired, causes wrinkles and destroys vitamins