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Losing weight when you're NOT on a diet can be a problem.

It's common to lose weight at stressful times in life such as when a loved one dies or a relationship breaks up. There's no medical reason for it, but a loss of appetite contributes. As you start to eat properly again your weight will go back on.

However, if you’re losing weight without planning to, this may indicate there's something medically wrong. Losing 5% to 10% of your body weight over 3 to 6 months without dieting is a health risk. A 70kg (11 stone) person would be at nutritional risk if they lost between 4kg to 7kg (8lbs to 1 stone in weight) over 3 to 6 months.

Weight loss and illness

If you are losing weight without even trying to it may be because of a medical condition or illness, and this can be worse if your appetite is affected too.

Around 40% of people with cancer have unintended weight loss when they are diagnosed, but there are other medical reasons for weight loss, too. Depression and thyroid problems can also cause it.

Losing weight fast makes it harder to get better. You'll respond to treatment better if you are a healthier weight and are getting the right nutrients from a varied diet.

Even if you were overweight before, the weight that you lose will not just be fat but will also include muscle loss too. Losing muscle affects your strength and immune system.

"If you have an illness you need more energy to fight it off," says Sarah Owen, clinical dietitian and spokesperson for the British Dietetic Association. "It may be that you feel you're not able to consume as much food as usual, but it's important to increase your energy intake as your body needs it to repair itself."

Cancer Research UK says eating properly can help you cope with treatment and side-effects, handle the most beneficial dose of certain treatments, and help you recover and heal faster.

These tips may help minimise weight loss:

1. Weigh regularly

Weight loss may be easy to miss. Keep a regular eye on your weight so you can monitor fluctuations and know whether your attempts to put on weight are paying off.

"Weigh yourself once a week on the same scales at the same time. If you are starting to regain 500g/1lb a week you are on the right track," says Sarah.

2. Mini meals

Mini meals are often more appealing if your appetite is low.

"Large plates of food can be overwhelming and off putting. Aim to have a small snack between meals and try to have a dessert after lunch and evening meal," says registered dietitian and British Dietetic Association spokesperson Michelle McGuinness.  

Three meals and 3 snacks a day would be ideal. Eat whenever you feel even a tiny bit peckish.

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