Can you eat yourself fitter?

PowerBar Performance Energize Berry Blast, £1.35 (www.fuelsport.co.uk)

ENERGY BARS

GOOD FOR...

Refuelling on the move. If you want to replace energy lost during exercise, you need something that's speedily digested, which is where bars come in.

WATCH OUT FOR...

Added ingredients. 'The best bars are the simplest - added fats, protein or fibre slow down the energy delivery of carbs, which are the most important element,' says Asker Jeukendrup, director of the Human Performance Laboratory at the University Of Birmingham. So why not just have a banana? Energy bars deliver more calories per gram and are also more convenient to carry. But try not to graze on them for the sake of it. 'You don't need them for any exercise session under 60 minutes,' adds Jeukendrup.

PowerBar Performance Energize Berry Blast, £1.35 (www.fuelsport.co.uk).

Powerade Aqua+ (hypotonic) 99p, Tesco

SPORTS DRINKS

GOOD FOR...

'Sports drinks are great at fuelling you up if you exercise first thing in the morning and don't eat before you set off,' says Griffin. And, though you don't strictly need them for shorter sessions, they can be useful when conditions get hot and sticky. 'A sports drink will replace sodium and increase your rate of hydration faster than water,' says Griffin.

HOW TO CHOOSE...

If you exercise for less than an hour or are calorie counting, opt for a hypotonic drink. 'They contain fewer carbs, which makes them good if you have weight loss in mind,' says Griffin. Isotonic drinks should be used for sessions of more than an hour, if it's hot or if you're sweating lots, so they're ideal after a Bikram yoga session. They contain more carbs for energy, plus electrolytes such as sodium, which you lose when you sweat. If you're super-serious about improving your performance, carbheavy, hypertonic drinks are best.

WATCH OUT FOR...

Caffeine. It's safe, but only if you're used to caffeinated drinks or increase your intake gradually,' says Griffin. 'Caffeine doesn't suit everyone, just as the balance of ingredients in one drink might suit one person better than another. That's why you shouldn't try a new drink on the day of a race. Experiment to see which suits you beforehand.'

Powerade Aqua+ (hypotonic) 99p, Tesco; Taut Lemon Endurance (isotonic), £1.09, Tesco. Both are free from artificial colours, preservatives, flavours and sweeteners. Both are free from artificial colours, preservatives, flavours and sweeteners.

Science In Sport Isotonic GO-Gel £1, is an easily digestible gel (www.scienceinsport.com)

GELS

GOOD FOR...

Endurance exercisers. 'Gel sachets are an easy and convenient source of energising carbohydrates if you're exercising for long periods,' says Griffin. According to Runner's World, if you're going to be running for between 90 and 120 minutes, one gel should get you through, taken after about 50 minutes. If you're running for more than two hours, take two gels - the first after about 45 minutes and then another after about 90 minutes.

WATCH OUT FOR...

Cramp. Your body needs water to process the carbohydrates in most gels, and will take it from any source it can, including your muscles, which can give you cramp. To use them well, 'you need to drink water or they can actually dehydrate you,' says Griffin.

Science In Sport Isotonic GO-Gel £1, is an easily digestible gel (www.scienceinsport.com)

Lucozade Sport Strawberry Flapjack Recovery Bar, £18.90 for 12 (www. lucozadeshop.com)

PROTEIN PRODUCTS

GOOD FOR...

Frequent exercisers and anyone serious about having toned muscles. 'Purer protein products (which contain fewer or no carbs) are for when your goal is lean muscle mass,' says Griffin. 'Protein products are the faster way to toned, shapely muscles and will help you see quicker results if you're doing weight-training.' However, for normal-intensity exercise of less than an hour, you should get enough protein from your diet. Protein also plays an important role in helping muscle recovery, enabling you to exercise more frequently. 'Eat or drink your chosen product within an hour of finishing exercising,' advises Jeukendrup.

WATCH OUT FOR...

Carbs. It's important that a recovery product also contains carbohydrate - it will replace energy lost during your workout and increase insulin, which aids your recovery,' says Jeukendrup.

Maximuscle Promax Protein Powder, £18.99 (www. maximuscle.com); For Goodness Shakes! Banana Milkshake, £1.28 (www. forgoodnessshakes. com); Herbalife Personalized Protein Powder, £19.85 (0845 056 0606); Lucozade Sport Strawberry Flapjack Recovery Bar, £18.90 for 12 (www. lucozadeshop.com).