Natalie Harvey from Lowestoft will appear on Channel 4's Joe Wicks The Body Coach after committing to his 90-Day Body Confidence Challenge. How easy did the rugby playing working mum find it to swap pizza for kale and booze for water?

As a loose-head prop for Southwold Swallows, size was an advantage for Natalie Harvey.

But although being a size 16 helped on the rugby pitch, off it, Natalie felt unhappy with her fitness levels and weight and when her teammates talked about applying to be on 'Body Coach' Joe Wicks' new TV programme, she quickly applied.

'When I play rugby I'm in the scrum at the front and being a bit bigger is beneficial,' said Natalie, 31, who lives in Lowestoft with husband Del, 35, children Harvey, 12 and Oscar, four, and who has a stepson Joshua, 13, 'but when I was off the pitch, I didn't feel so great. I just wanted to find a way to lose weight I could stick to.

'I'd tried almost every diet going and all the clubs out there but nothing worked. I loved pizza, wine, biscuits, chocolate…all the lovely things that are bad for you. I'm a busy working mum and I just don't have time to join a gym or cook meals that take hours. It was easy to throw chicken nuggets and chips in the oven for everyone. The rugby became a bit of an excuse for being bigger.

'There are lots of reasons why I wanted to lose weight but one is that my brother is getting married in June and I didn't want to be a fat bridesmaid!'

Enter Joe Wicks. Health and fitness guru Joe is a social media sensation who's reshaped the bodies of thousands of people across the UK with his 90-day body confidence plan which involves entering a world of high-intensity exercise, nutrient-dense dinners and a complete change of attitude when it comes to food.

'I was amazed to get a phone call from the production company but I didn't let myself get too excited, I just waited to see what would happen. Each stage I got through, I was a bit more hopeful,' said Natalie, who works for Alicat Workboats in Great Yarmouth as an accounts assistant.

'When I was told that I'd got through, I couldn't believe it. I was so excited - and a bit scared!'

Natalie is one of eight people taking part in Joe Wicks The Body Coach a new series from Channel 4 which aims to help eight people battling with weight and health issues to transform their lives.

'From the beginning, I knew I had to stick to the plan, which was tailored especially for me. It involved eating really healthily, drinking only water and doing exercises in cycles – the first five days were absolutely horrible,' laughed Natalie, who admits she had a 'permanent headache for days'.

'You need to be very disciplined and you need to be committed to doing what your plan tells you to. I shocked myself – I stuck to it. There wasn't a single time that I fell off the wagon, I just kept going, through my birthday, a wedding, my friend's 30th birthday…it was hard, especially seeing what other people were eating and drinking!

'Don't get me wrong, I think that if I hadn't known there would be before and after shots on TV, I'd have given up in those first few days. But really quickly, I started to feel great – my skin felt so soft, I had so much energy, I didn't get tired as quickly as I used to, I was happier.

'I didn't have a clue that eating well and exercising could make you feel like that – even my nails grow quicker now!'

Natalie had around six personal coaching sessions with Joe who met her family and took her for exercise sessions on Lowestoft beach. Throughout, her competitive streak kept her going: 'I remember when I went to have the 'before' filming session and I was standing there in a sports bra and shorts and I was fine when I was there but when I got back in the car with my husband I cried for about an hour,' she said.

'He loves me whatever size I am, but I didn't. It was time to make a change and Joe helped me to do that. He was so supportive, so encouraging. He's really lovely and he was great with my kids. When Oscar is in the supermarket and sees Joe's books he says 'that's my friend Joe!''

Natalie is still following Joe's advice although she allows herself treats now and then. When her three months were up, the first contraband that passed her lips was a glass of prosecco.

'It was delicious!' she laughs, 'and then I had a kebab! The difference is now I know how to eat and exercise so that I can have occasional treats. Doing the show was one of the best things I've ever done. It's changed everything. I can't recommend it enough.'

Natalie's typical day:

Get up half an hour earlier than the rest of the family and exercise: 25 minutes of HIIT (see video) or weights (five days a week, two rest days).

Breakfast: A carbohydrate-filled breakfast – Natalie's favourite was protein pancakes with protein shake powder, bananas, porridge oats, raspberries and almond oil and cooked in coconut oil. The pancakes were served with natural yoghurt and raspberries.

Lunch: Chicken cashew curry eaten with kale, broccoli and mange tout instead of rice.

Dinner: Joe's chicken pie – a filling of chicken, onions, garlic, spinach and cream with a topping of crumbled filo pastry, served with greens.

Snacks: Nuts or beef jerky.

* Episode one is on Channel 4 on February 13 at 8pm and then on demand.