At first, Scott Brown didn't realise the extent of his midlife weight gain.

It was subtle to begin with – the gradual tightening of his waistband – but as time went by, the number on the scales continued to climb.

'Without really noticing, over the years, I had gained weight, and I wasn't happy about it,' says Scott, now 55.

By his mid‑50s and at his heaviest, Scott weighed 17st 8lb and was suffering from severe back pain and nerve pain, which he believes were made worse by the excess fat he was carrying.

At just under 6ft tall, this put his BMI at 33.7, which is in the obese category.

'With me being so overweight, it was like I was carrying two full suitcases with me everywhere I went. That is an awful lot of weight to be carrying around on your joints and muscles,' he says. 'I felt like I was tailing off physically.'

It made little sense: his diet consisted of home-cooked meals and fresh fruit and vegetables, and he was far from lazy, often waking up early for long runs and bike rides.

However, he soon realised that his hearty family meals, such as spaghetti bolognese, lasagne and roast dinners, contained lots of carbohydrates and fats – and he had got into the habit of drinking more than he realised.

'My wife and I are very sociable, and we love spending time with family and friends, often around a table, enjoying good food and wine,' he says.

'Often, I would enjoy a glass of wine while cooking and would sometimes have a few more with dinner. It became a bit of an unconscious habit.'

Then, two years ago, Scott came across a solution that helped him lose five stone – and, for the first time in his life, actually keep it off.

The Fast 800 Keto diet, pioneered by the late British broadcaster and Daily Mail columnist Dr Michael Mosley, is a rapid weight-loss programme that involves reducing carbohydrate intake to transition the body's metabolism from burning sugar primarily to burning fat.

By his mid‑50s, Scott weighed just over 17 and a half stone and was suffering from severe back and nerve pain, which he believes were made worse by the excess fat he was carrying

Scott is now a healthy 12 stone 12 pounds having maintained his weight loss for two years

The plan incorporates an intermittent fasting pattern – periods of eating and not eating – and is recommended as a short-term intensive phase for a maximum of 12 weeks.

The online programme costs around £30 per month for the first three months and transitions into an ongoing rolling membership of £12 per month, guiding users toward a sustainable, low-carb, Mediterranean-style way of life.

'A family member had already done the plan and recommended it to me,' says Scott.

'When you sign up, you get sent recipes, meal plans and shopping lists so you can buy the food and cook the meals yourself.

'I really enjoy cooking and hate food waste, so I liked the idea of being able to shop for exactly what I needed each week and follow the recipes.'

On The Fast 800 programme, alcohol is strongly discouraged and if you choose to drink occasionally, you must count those calories into your daily 800-calorie limit. For this reason, Scott, from Sussex, decided to cut alcohol out of his life, replacing it with fruit teas, kombucha and very low calorie alcohol free lager.

'I knew that alcohol had been a big part of our social lives, so I wondered how this might impact me.

'However, I was serious about losing the weight I'd gained over the years and I decided that I was ready to give it a go, despite a bit of anxiety.'

Just weeks after starting the plan, which saw him eating around 800 to 900 calories a day, Scott started to see his weight drop.

'I fully embraced the programme and used its shopping lists to form the basis of our weekly online shop, adding in a few family favourites for the children.

'I meticulously stuck to the measurements but managed to make most of the recipes work for the whole family, as I didn't really want to cook two different meals. '

Scott made a few clever changes, cooking a bolognese for his family but swapping his pasta for courgetti spaghetti.

'Without really noticing, over the years, I had gained weight and I wasn't happy about it,' says Scott

'With me being so overweight, it was like I was carrying two full suitcases with me everywhere I went,' Scott says

He swapped his old breakfast of sugary granola for plain Greek yoghurt and his usual sandwiches for smoked salmon, spinach or chicken and salad.

But first, he had to overcome what is known as 'keto flu' - where the body is wracked with hunger pangs.

'For the first couple of days, I was suffering from brain fog - trouble concentrating, forgetfulness and mental fatigue,' he says.

'But as time went on, I found I didn't feel hungry at all, even though I was only eating around 800 calories a day.'

After two months of following the strict programme, he had already lost three stone.

'The results were really dramatic,' he says. 'Once I started losing weight, it became a habit.'

He was already very active, but realised that before, he was exercising to 'undo' his overeating from the previous day.

He was now enjoying his time at the gym, focusing on weight training as well as getting outside for mountain hikes and endurance runs. He now goes gym twice a week and enjoys a weekly 15km run.

'After the first three stone, the weight loss continued at a steadier rate over the next year,' he says.

'I continued riding my bike and running throughout the whole process but I noticed that I felt lighter and was more energised having lost weight.

'The lifestyle suited me, and I decided to continue with the programme beyond the first 12 weeks as I was determined to maintain this healthy weight and fitness level.'

After an intensive 12-week Fast 800 Keto phase, Scott moved on to the programme's 'Way of Life' maintenance plan, which he has now been following as a long‑term way of eating.

Scott has recently completed a full marathon and plans to continue the maintenance programme to stay at his current weight

'I'm much more confident, which comes from feeling really good all round,' Scott says

Unlike the strict, low-calorie Keto phase, the Way of Life programme involves eating around 2,000 calories a day – made up of healthy fats, plenty of protein and lots of fibre. It is tailored to maintaining a healthy weight, rather than creating a big deficit.

Over the past two and a half years, Scott has shrunk to 12st 12lb, putting his BMI at a healthy 24.6.

'One of the biggest changes is how easy buying new clothes is. I can just buy medium clothes online, and I know they're going to fit,' he says.

'It's not just the initial part about weight loss - it's about a sustainable lifestyle and being the best version of myself.

'Maintaining a healthy weight is almost harder because you’re not getting that reward of getting on the scales and losing weight.

'You have to really pat yourself on the back when you’ve maintained your weight.'

Although he still occasionally experiences muscle spasms, Scott says his chronic back pain is now ‘nowhere near as frequent as it used to be'.

He has recently completed a marathon and plans to complete the Fast 800 keto diet for a second time to achieve his goal weight of 12st.

However, as with any rapid weight loss plan, the programme is not without its critics.

Some experts have warned that consuming a very low-calorie intake of 800 calories per day carries risks of nutritional deficiencies, fatigue and potential muscle loss if not carefully managed.

Registered nutritionist Jenna Hope says: 'The Fast 800 diet is a highly restrictive diet which can pose a risk of malnutrition, low fibre intake and nutritional deficiencies.

'While the diet is used in extreme cases, it's always recommended to seek advice from a health care professional and your GP.

'It's also important to highlight that highly restrictive diets are not sustainable and weight regain is likely when it's not done under controlled conditions.'

But for Scott, the results have been life-changing.

'I'm much more confident, which comes from feeling really good all round,' he says.

'I never thought I'd be able to say this, but I'm also starting to feel that energy that I had when I was in my 20s come back.

'People can't help but comment on how different I look. It feels really good to hear people say, "You look really well."

'When people say, "I'm doing the Fast 800" or "I've run a half marathon because of you" it's brilliant - it makes me realise this journey isn't just about me; it's about helping others change their lives too.'