Eat yourself well with The Detox Kitchen Bible, Kate Whiting suggests

But they're not meeting me to preach about going wheat, dairy and sugar-free: they're hoping to share the message that cutting down on those foods just 80% of the time will give you more energy - and help you to live healthily without the need for crash diets.

"Our detox is not as you'd imagine, it's not a strict regime, it's a lifestyle change," says Lily, who's multitasking as she speaks, breastfeeding her six-month-old son Finley and sipping on a hot chocolate ("half milk, half water"), while her dog Rudy sitting obediently at her feet.

"We're saying, 'If you eat really well 80% of the time, then 20% of the time, you can go out and have some drinks, indulge and have whatever you want'. Once you understand that and listen to your body, you don't need to worry, because you know what to cook that makes you feel good.

"It's really important that people become connected again with what they're eating."

The book is split roughly in two parts, with delicious, healthy recipes from Simpson making up the first half, which all come with a list of the health conditions they can be useful for, and the second part is nutrition advice from Hobson, with suggested detox plans designed to help your heart, bones, digestive system, mind, weight and immunity, among other things.

Nutritionist Hobson says the best approach is to embrace healthy eating as a whole lifestyle, rather than a diet, and go slowly.

"The way that people end up not doing anything is they just try and do it all at once. Take small steps. Take one recipe a night and start with cooking something fresh," he says. "If you're eating lots of sugar, don't give it up straight away, just eat one biscuit instead of two.

"We're not telling anyone to do anything we don't do. I like a glass of wine in the evenings, but I know that most of the time, my food is spot on, I exercise, I try and get as much sleep as I can, you've got to try and find a balance and it's different for everybody."

Simpson is all about the balance, too. "I eat butter on toast for breakfast, I have a really filling lunch and a healthy dinner and then I probably have a glass of wine and a chocolate, so it's kind of that balance," she explains.

"We hate the word 'diet' - I've never been on a diet in my life. I tried to do a juice one once, where you have juice all day, and by about 10 o'clock, I was like, 'I need something to chew', I'm not into all that strange stuff."

Simpson, who set up the London-based meal delivery service Detox Kitchen (detoxkitchen.co.uk) with Hobson three years ago, whose fans include Elle McPherson and Sophie Dahl, knows from her own experience just how much what she eats impacts on how she feels - and looks.

Having grown up eating home-cooked meals, she let her healthy habits slide when she moved away from home. "When I moved to London, I got IBS and I had stomach ulcers, which played havoc with my skin," she recalls. "It was really when I started understanding that very strong link between food and how you feel that things started to change.

"Beetroot makes my stomach feel dodgy because it triggers my IBS, so I tried to cut down and not eat as much. And if I have a breakout on my skin, I know exactly what to do. I totally cut out dairy and I try and reduce the amount of sugar in my diet.

"As soon as I start eating well again, I can think straight and feel less foggy, but a lot of people don't understand how great they can feel just by eating good food. I have days where I eat rubbish food, but I know how to make myself feel better."

Sugar has been demonised recently, but Hobson believes it's "not bad" in small quantities - and make sure you enjoy it while you're eating it.

"I say to clients, if you're going to have some sugar, don't do that thing where you give yourself a tiny little bit of cake and keep going back into the fridge and eating it really quickly.

"Take a piece, put it on a plate, sit down with it, enjoy it, and then you're done. I had a client who had to put the rest of the cake and the biscuits in the bin and put washing up liquid on them so she couldn't go back to them.

"Some of the unhealthiest people I've seen are walking around 'health food' shops. They follow really strict diets, they've eradicated everything, they're living on supplements, they look so tired, they've just got it wrong."

Feeling inspired? Here's one of their recipes to get started with. 

Butternut, coconut and chilli soup (Serves 2)

1 butternut squash

1tsp crushed dried chilli

1 red onion, finely sliced

600ml vegetable stock

200ml coconut milk

Salt and pepper

1. Preheat your oven to 180C/fan 160C/gas 4. Line a baking tray with greaseproof paper.

2. Peel the butternut squash and cut it lengthways in half. Scoop out the seeds and fibres, then cut the flesh into 2.5cm pieces. Spread the pieces on the baking tray and roast for 15 minutes.

3. Remove the tray from the oven and scatter the chilli and onion over the pieces of squash. Roast for a further 10 minutes. Remove from the oven and allow to cool for a few minutes.

4. Pour the stock into a medium saucepan and bring to the boil, then turn the heat to low. Stir in the coconut milk and warm for two minutes. Remove from the heat.

5. Put the squash, onions and chilli in a blender and add the coconut milk/stock. Blitz until smooth, then season to taste. Serve hot.

The Detox Kitchen Bible is published by Bloomsbury, priced £25.