If you're really going to get and stay in shape, it's important to get your facts straight about fat and muscle, so let's take a look at some of the myths and turn them into facts.
Myth 1: Muscle weighs more than fat
If your diet plateaus after a few weeks, you may believe it's because you're gaining muscle because "muscle weighs more than fat". Sadly this just isn't true. If you put a pound of fat on the scales, it will weigh the same as a pound of muscle.
It's true that muscle is more dense than fat, so a bodybuilder may be relatively heavy with virtually no body fat, but building muscle takes time and it's unlikely you've built several pounds-worth of muscle already. It's more likely your diet has lost its mojo. Give your regime a boost - try a different class or machine, and tweak your diet.
Myth 2: You can turn fat into muscle by exercising
Again, unfortunately this just isn't true. A fat cell can't be turned into a muscle cell, no matter how much exercise you do. You build muscle by working your existing muscles. If you want to speed this process up, try a bit of strength training. If you're worried that'll turn you into a she-man, read on!
Myth 3: Doing weights makes you bulky
Most women are after a lean, toned look rather than becoming muscle-bound, so they focus on cardio instead of weights. But they're missing out. Building muscle - by which I mean a toned stomach and limbs, not bulging biceps - makes you burn more calories by raising your resting metabolic rate.
Unless you have guy-levels of testosterone, you won't grow enormous muscles by strength training. Female bodybuilders only look like they do by training like crazy and eating an incredibly controlled diet. It honestly won't happen to you by accident - you'll just gain that fabulous toned look you were after.
Myth 4: You can damage your bones by doing weights
This is simply not true. Weight training does not damage your bones - quite the reverse. You won't snap a thigh bone by doing a leg press - in fact you'll be less likely to break a bone. Research shows that strength training can increase bone mineral density by 13% in six months, which reduces your risk of osteoporosis.
Myth 5: Fat makes you fat
We were sold a lie in the 80s when they told us to go low-fat. Fat does not make you fat. In fact, low- fat diets have been shown to be pretty ineffective when it comes to weight loss.
By all means avoid trans fats - the hydrogenated fats you find in a lot of processed foods - but don't be afraid to eat healthy fats such as olive oil, avocados, nuts, seeds and oily fish. They help control your insulin levels, keep you feeling fuller for longer and don't slow down your weight loss.
Patricia Carswell is a freelance journalist and award-winning blogger specialising in health and fitness. She has written for the Daily Telegraph, the Guardian, the Observer, the Independent, Times Online, the Daily Mail, the Daily Express, Metro and a wide variety of national magazines and websites. She blogs at www.sportyoverforty.com and www.girlontheriver.com and has a particular interest in fitness for the over-40s.