TOP tips from 2016 best-selling author Joe Wicks, The Body Coach, in his Lean in 15 book:

1 Prep like a boss

"You've got to prep like a boss, which means preparing your own meals, so when you're leaving the house, you've got your lunch and your dinner sorted."

2 Drink more water

"A lot of people don't drink enough water, and a hydrated body burns more fat, so try and drink two to four litres a day."

3 Do HIIT cardio

"Twenty minutes a day, four to five days a week. It's high-intensity training and you're going to burn loads of calories."

4 Take before and after pictures

"You can keep them for yourself, but it's a really great way of seeing your progress over time, as opposed to looking in the mirror and thinking, 'I haven't changed, I look exactly the same', but really you probably have, you just don't know it."

5 Allow yourself treats

"Don't be afraid to get a bit guilty on the weekends. If you like having a drink and if you like treating yourself to a little tub of ice-cream, it's fine - you know - moderation, balance."