Q: My flatmate runs and runs but she still has a muffin top and just doesn't lose weight. I, on the other hand, am a normal body weight. I lift weights and do plenty of cardio because I want to have muscles that look defined at rest. Neither of us is achieving our goals. What are we doing wrong? Is it our diet that is letting us down?

A: Your flatmate, to put it bluntly, is probably eating more than she realises. Running is great exercise, good for your body and your mind, but running alone will not make you slim and burn off tummy fat.

It is important to remember that about 60 per cent of the calories we burn are spent on keeping our organs such as our brain, liver, heart and kidneys ticking over and doing their stuff. A further 10 per cent is used in the process of digestion. The remaining 30 per cent of the calories we eat is used for generally getting around during the day (from hauling ourselves out of bed and getting dressed to dashing for the bus, for example) and in deliberate exercise, such as running.

It is a sobering thought that, according to scientists at Tufts University, near Boston, Massachusetts, the calorie needs of a runner and non-runner are not drastically different and that even by the end of a 26-mile marathon (which I doubt your flatmate is doing each night), she would burn off only one pound of fat, which is equivalent to about 3,500 stored calories.

To put it another way, a woman between 9 and 11 stone in weight burns between 300 and 400 calories for a half-hour jog. You need only to have one fruit smoothie (150 calories) and a blueberry muffin (450 calories) to completely negate the effects of all that effort.

Her first step, therefore, is to keep an accurate record of everything that she eats and drinks each day for a week. This means every morsel that passes her lips and every glug of juice, latte, cappuccino, tea, fizzy drink, squash or alcohol - along with the serving sizes of each.

It is usually quite easy to see where cutbacks can be made to lower calorie intake. If she is running and lowering her excess calories, she should burn fat, including from her stomach.

As for your own query, there are two issues here. One is that women are not really designed to have David Beckham-style physiques, where muscles are obvious and rippling, even when at rest.

Our hormonal balances mean that we simply cannot build as much muscle as men and we have a naturally higher body fat compared with them. This gives the muscles we do develop a soft and curvy covering.

I appreciate that the very honed Madonna look is possible for women, but it takes hours and hours of exercise to achieve, combined with an incredibly strict eating regime, and is not easy to maintain while living a normal life.

I hope that you don't mind me saying, but maybe you can think about redefining your goals on how you would like to look. A fit and slim body is a great goal and is hard enough to attain for women who are juggling the usual pressures of everyday life.

E-mail Amanda at amanda.ursell@thetimes.co.uk

Keep fit, not fat: good exercise and diet

1. To help to burn body fat, even when at rest, your friend needs to combine her running with some strength training exercises to raise her general metabolic rate. She can find some great strength training exercises at www.strongwomen.com that can be done at home.

2. If doing less than 90 minutes of exercise a day, you just need to eat in a healthy and balanced way every day to fuel your fitness routine. Skipping meals will reduce the efficiency of your workout.

3. Try to have a small snack such as a piece of fruit or yoghurt a couple of hours before exercise and a balanced meal (or at the very least, a snack such as a banana and fromage frais, for example) within a couple of hours of finishing.

4. Leave 3-4 hours after eating your main meal before exercising.

5. Lots of people fall into the trap of “treating” themselves for having done some exercise and tuck into chocolate, crisps and drinks straight after. If you are trying to lose weight this is an own-goal; stop it.

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