Melanie Leyshon is the editor of Healthy Food Guide magazine. She's a flexitarian and couldn’t get through the week without yogurt and yoga.

A former British modern pentathlete, Greg now coaches celebs for tough sporting challenges. He explains why setting a goal is so important for weight loss

How is your health right now?
On a scale of one to 10, I’d say 10. I exercise at least five times a week and eat a healthy diet. There’s a direct relation between physical activity and your health. Research shows the more you exercise, the fewer coughs and colds you’ll get, or at least they won’t be as prolonged. Exercise helps your respiratory system fight bugs.

How do you stay motivated now that you’re no longer a professional athlete?
I practise what I preach. Being successful is about setting realistic goals. They shouldn’t just be ‘I want to get fitter,’ or ‘I want to lose weight.’ You need to set small goals and a timetable.

What’s your own fitness plan?
I follow the exercise for the project I’m working on. For example, earlier this year I worked with comedian Jo Brand on her Hell Of A Walk and DJ Greg James for his triathlon challenge. I actually find it easier to work out the busier I am, as you have to target a time slot and put it in the diary.

Did you change your diet when you stopped being a professional athlete?
My diet itself didn’t change dramatically, just the calorie content. When you’re exercising intensely you’re eating to replenish lost energy. When you stop, you can have the same healthy diet, but don’t need to eat as much. I see a lot of ex-professional athletes who are now incredibly overweight because they haven’t adjusted their calorie intake. It’s all about the difference between calorie expenditure and consumption.

Any weight issues?
I’ve never been overweight, but my weight fluctuates depending on the sport I’m doing. When I was swimming the channel [training David Walliams] I needed to put on weight, so I gained 8kg. But I lost the same amount when I was running a marathon in the Sahara desert.

What’s your best bit of diet advice?
Make it yourself. The biggest problem is eating too much processed food that contains sugar. When my kids see my wife making her homemade bread they actually ask, where’s the sugar? It’s in so many foods, from sandwiches to salads and ready meals, it’s just expected to be an ingredient.

Do you cook?
As a family, yes. I enjoy cooking, although I’m no Gordon Ramsay, but my wife is a very good cook.

What do you eat for an energy boost?
I don’t go for sugary snacks that give an instant hit, but for complex carbs or protein that increases satiety – a glass of milk or a seed-based bar.

And for a treat?
It’s about balance and moderation and not excluding anything. I love a doughnut and tease my kids, telling them the strawberry jam counts as one of my five-a-day. We shouldn’t think of any food, including chocolate or alcohol, as bad. Food should be about happiness and not about the misery of exclusion.

Do you have a weight-loss tip?
Identify what you’re trying to achieve. Just saying you want to eat more healthily has no end goal. But be realistic. The biggest barrier to losing weight is time – people try to do too much too soon (saying, for example, ‘I want to lose 6st by February’). Losing it is possible, but give yourself time.

What’s your general attitude to health?
A healthy lifestyle and diet is for life, it’s not just something you address in middle age. It’s important from birth all the way through to old age.

And your top piece of health advice?
Do more physical activity, for sure. We need to be moving more and more often. That means walking, taking the stairs, parking as far away from an entrance as possible. Being an ‘athletic potato’ and doing a 30-minute workout a day is all very well, but that’s not enough if you’re inactive for the rest of the day. There are great advances around health – activity trackers are motivational as they show you how little you’re doing! A lot of people are surprised to find they’re not as active as they thought.

You’ve just written a book about pregnancy and exercise. How did that come about?
I’ve got three young children and when my wife was pregnant there was no information about exercising. I don’t mean it was limited – it was non-existent. There are also lots of old wives’ tales around fitness and pregnancy, such as the ludicrous claim that the umbilical cord can get wrapped around the baby’s neck if you exercise. I wanted to dispel those scare stories. The book has two main aspects: what’s safe to do, and myth busting. It also looks at optimising your fertility and improving your chance of getting pregnant. It’s evidence and science based.

Three things I love

STRAWBERRIES The fruit sugars they contain are good for you

9BAR This seeded bar is my go-to snack

MY FITBIT SURGE to track my activity and sleep

Related article: How I stay healthy: Amanda Hamilton