But scientists are saying these dishes could have surprising health benefits, thanks to the chemical reactions that take place when food is left overnight.

 

From glowing skin to trimmer waists, we reveal why yesterday's supper could be so good for you.

 

 

Rice, when chilled overnight can contain up to 60 per cent fewer calories than when freshly cooked -- potentially dropping from 130 calories per 100g to just 52. But you need to cook it in the right way, according to research presented to the American Chemical Society.

 

When the water is boiling, before the rice is added, pour a little coconut⁴ oil into the pan -- about 3 percent of the weight of the rice you're using. When cooked, leave in the fridge for 12 hours to hugely reduce the calories.

 

When cooked rice is eaten, its starch⁵ is turned into the sugar -- glucose⁶ -- by the body and converted into fat if not burned off.

 

However, when rice is chilled, its starch becomes what is called 'resistant⁷ starch', which the body cannot digest. This means it is not included in the calorie count.

 

 

Bone broth⁸ is a big nutritional⁹ trend. Low-calorie and rich-tasting, the soup also appears to be packed with ingredients to make your skin glow.

 

As the name suggests, it contains the bones from meat -- beef, lamb or chicken -- cooked with water and ideally a little cider vinegar to help the process.

 

Collagen from the bones breaks down into gelatin, which is easy to digest and excellent for the skin.

 

 

We all know that cooking vegetables for longer removes vitamin C. But some believe that people with digestive problems, such as irritable¹⁰ bowel¹¹ syndrome¹², ought to overcook vegetables containing insoluble fibre, such as onions and garlic, which can cause bloating. Reheating the next day could supposedly soften¹³ them further.

 

Dr Christie is unconvinced. 'Sorry, you aren't going to make any real difference to the molecular¹⁴ structure,' she says.

 

A 1992 UK study found cooked potatoes contained just 7 percent resistant starch (the indigestible type). But when cooled, it jumped to 13 percent.

 

Separate research has discovered this starch has the same benefits as dietary fibre, that protects against colon¹⁶ cancer, increases the feeling of fullness and might even reduce fat storage.

 

'When potatoes are cooled after heating, the starch molecules¹⁷ expand and crystallise,' says Dr Christie. 'Once swallowed, this resistant starch is treated like fibre by the digestive system.'

 

 

Even the fieriest¹⁸ curry is gentler the next day. What's more, it may be easier to digest and contain more nutrients¹⁹ as the meat tenderises overnight.

 

'If you leave a meat curry for a few hours, the animal proteins degrade and become softer,' says Dr Christie.

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