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Amanda is Healthy Food Guide's nutrition editor with a degree in nutrition and a post-grad diploma in dietetics. She is a member of the British Dietetic Association, The Nutrition Society and The Guild of Food...

If you’ve left your honing your holiday shape to the last minute, you may be considering a crash diet. This summer’s ‘go to’ diet is the GM plan – an extreme seven-day, quite bizarre eating plan devised by General Motors in America to help their employees shift weight fast.

It’s a ‘very low calorie diet’ (VLCD). You eat very little over seven challenging days, and it’s been likened to the cabbage diet. There’s a fruit only day, a potato with butter for breakfast day, plus vegetable days that exclude peas, corn or carrots.

Unsurprisingly, it leads to rapid weight loss, but this is mainly from burning glycogen stores in the liver and muscles, water loss and losing some lean muscle. Only around 1lb of this loss will be fat.

Here are five reasons you need to take that pre-holiday crash diet off your to-do list:

1. The weight loss on the scales is likely to lull you into a false sense of security. Once you’re on holiday, the chances are your week of self-denial will rebound with overindulgence and a guilty conscience – the last thing you need on your well-earned break.

2. As soon as you start eating normally again, your glycogen stores will be replenished and the number on the scales will shoot up, whether you’re eating healthily or otherwise. This could wreck your poolside confidence.

3. While your insulin response may temporarily improve through what essentially is a fasting diet, there is no long-term benefit from such a short, sharp, one-off period of calorie deprivation.

4. Many women in the UK are already low in nutrients, including iron, which can lead to feeling tired and stressed. Compounding this with a restricted crash diet risks you feeling worn out and not getting the most from your summer break.

5. Crash diets inevitably put off the unpalatable truth that dietary and lifestyle changes need to be made for the long term, and not just a week. If you want to get in great shape for your holiday, start now with small, sensible changes, so that by 2018 you’ll be beach ready and ready for anything.