When you eat rice that’s been boiled with a little bit of oil when cooked, you absorb 50 per cent fewer of its kilojoules, compared to eating freshly cooked rice. It’s because both the oil and the cooling process change the structure of the rice’s starch, making it more resistant to the body’s digestive enzymes.

Make it work: Cook the rice with a teaspoon of coconut oil (per half cup of rice) and refrigerate it for at least 12 hours, say researchers, who are yet to work out whether other oils create the same effect. And you don’t have to eat the rice cold – reheating it doesn’t alter the kilojoule-lowering properties.

Plus, day-old rice is great for whipping up delicious fried rice! Freshly-cooked rice that’s warm and moist may turn your fried rice dish soggy, whereas rice that’s been sitting in the fridge overnight has enough time to dry out just enough for a good, chewy texture. Try our best fried rice recipes here!

Cooked and left to cool, potatoes become a good source of resistant starch. Resistant starch is fermented in the large intestine, which changes it into the short-chain fatty acids that promote a healthy bowel – and healthy gut bacteria is closely linked to good immune function.

As well as giving your immune system a boost, resistant starch could be a helpful tool for diabetics because of its ability to improve insulin sensitivity and lower blood sugar levels.

Make it work: Rather than reheating leftover potatoes, it’s best to eat them cold in a salad, because chilled potatoes contain more resistant starch than chilled-and-reheated ones. Try these potato salad recipes (ignore step 1 if you’re using leftover potatoes):  Ultimate Potato Salad, Smoked Salmon and Potato Salad.

Not only does the cooking process immediately increase a carrot’s levels of cancer-fighting antioxidants by 34 per cent, those levels keep rising for a few days afterwards. So eat them as leftovers and they’ll be even better for you. And the cooking method doesn’t matter – the antioxidants in carrots will rise regardless of whether you microwave, bake or boil them.

Make it work: If you’re going to boil the carrots when you cook them for the first time, leave them whole and chop them later. They’ll contain 25 per cent more falcarinol,a compound with anti-cancer properties, than carrots that are chopped before boiling. Try these yummy carrot recipes that your kids will love too.

When tomato-based sauces are cooked and then exposed to heat a second time, lycopene, the antioxidant tomatoes contain, is restructured in a way that makes it easier to absorb – and people with high levels of lycopene in their blood are 55 per cent less likely to experience a stroke. The researchers behind the finding say it’s because lycopene reduces inflammation and blood clot risk, which play a role in stroke risk.

Make it work: Add a dash of olive oil to the pasta sauce when you reheat it – the oil combined with the heat is what alters the shape of the lycopene molecules.

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Eat it after it’s been cooked, cooled and reheated and your blood sugar levels will only rise half as high post-meal, compared to when you eat pasta immediately after cooking it. And that matters, because keeping blood glucose levels in check is one way to minimise your risk of developing type 2 diabetes.

What’s the difference between freshly cooked and reheated pasta? Like leftover rice and potatoes, the starch in reheated pasta is more resistant to digestion, so it creates less of a blood sugar surge once you’ve eaten it.

Make it work: Choose wholegrain pasta to boost the benefit, after research linked a bigger wholegrain intake with a lower risk of type 2 diabetes. And remember that “saucy” pasta dishes store and reheat better than plain, cooked pasta, so think lasagne and olive oil or tomato-based penne and spaghetti dishes.

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