You're training regularly, but your diet could be draining you of energy and making things harder.
High glycaemic index (GI) foods make for unstable energy levels with their fast but short-lasting release, while insufficient carb or protein replenishment impairs muscle recovery.
Plus, not drinking enough of the right fluids can lead to chronic mild dehydration, causing fatigue. Here's how to avoid some common dietary pitfalls.
1. Guzzling a daily venti-gigantaccino
Your morning commute can seem less of a grind with a quick hit of caffeine and sugar.
But, as Nutritionist Kim Pearson (kim-pearson.com) says, "Giant cups of coffee might keep you going, but it's a quick fix that you'll pay for later with an energy crash."
An 11-week study* analysed purchases in major coffee chains, and found that the most popular choices, 'blended coffee drinks', contained on average 239kcal.
Drink one a day and researchers warn you'll be on track to gaining a stone and a half within a year.
Break it: Green and rooibos teas are rich in the antioxidants that help counteract the damaging effects of free radicals, released when you exercise. Pearson recommends pairing your drink with a Bounce Peanut Protein Ball (£1.49, bouncefoods.com), which is low GI and rich in peanut and whey protein.
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2. Skipping breakfast in favour of a lie-in
Energy is stored in the liver and muscles as glycogen. But four to six hours after eating, these reserves are exhausted; by breakfast time, you're running on empty.
Pearson says, "A good breakfast is essential to maintain energy throughout the day - but avoid cereals that are full of energy-spiking sugar and the empty calories of refined carbs."
Break it: Eat protein-rich eggs on wholegrain toast or sugar-free muesli. Really reluctant breakfasters can grab a protein shake with a palmful of unroasted nuts for on-the-go fuel.
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3. Improperly fuelling midday runs
A snack such as a banana will see you right before a lunchtime run, but even the busiest runners shouldn't neglect post-run fuelling.
Research suggests you eat 1.5g of carbs per kilogram of body weight within 30 minutes of exercise to restore glycogen reserves and prevent low blood sugar levels.
Break it: Mixing protein with carbs boosts muscle protein synthesis. "Go for ham salad sandwiches without mayo and an isotonic sports drink for extra carbs and electrolytes," says Mike Gleeson, professor of exercise biochemistry at Loughborough University.
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4. Bingeing on biscuits through the afternoon
Sugar binges give temporary highs, but these simple carbs and empty calories quickly lead to even lower lows. "Lots of sugar triggers insulin surges, causing plummeting energy levels," says sports nutritionist Anita Bean (anitabean.co.uk).
"Swapping sugary, high GI food for more nutritious low GI snacks means you'll have stable blood sugar and insulin levels. There's less risk of fat storage too: low GI carbs are more likely to be converted into glycogen instead of fat."
Break it: Fruit, wholemeal toast, nuts and yoghurt are all desk-friendly, low GI options.
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5. Having a few too many at the pub
You've trained hard, so you deserve to let your hair down. But "high-alcohol beers, spirits and caffeinated drinks all impede full rehydration", Gleeson says.
That means you'll have a worse hangover and a much harder time running the next day.
Break it: Alcohol is a valid option if you can't face mineral water: "Although it's a diuretic [which means it will make you pee more often], two per cent alcohol or less will not impair rehydration, so a beer shandy made with diet lemonade is a good choice for runners," says Gleeson.
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