Si and Dave decided to change their unhealthy ways after a friend who is also a doctor told the pair: 'Look lads, you are middle-aged and morbidly obese. You need to do something about it.'
'I was something like 40 per cent fat, my blood sugar was borderline for Type 2 diabetes and my cholesterol and blood pressure were way too high,' Dave admitted to the Express in 2016.
Si and Dave together in 2017, showing off the results of their dedication
'For me it was incremental. I probably put on a stone a decade which I think a lot of people do.'
Both men began making changes to their diet and upping their exercise routines, leading to an overall weight loss of around three and a half stone apiece.
'It's never too late to do something about it, you just need very small incremental steps, such as walking 500 yards more every day,' Si explained.
'It's not rocket science, it's not about massive changes. With lots of small changes you develop momentum, you can see the difference.'
The pair pictured in 2010, before they overhauled their lifestyles
So how can you lose weight on the Hairy Bikers' diet?We caught up with one half of the duo, Si, who gave us the lowdown on the Hairy Bikers' diet and how you can follow in their very successful footsteps...
Spice it upSi says: 'There are very few calories in spice. If you're clever with herbs and spices you can make fantastic dishes which have less calories.'
The Hairy Bikers boys weren't known for skinny salads or skimpy portions back in the day. But one thing they've taken from their love of food is that everything should taste great - even the healthy stuff. So, if you're dreading the thought of missing out on your family favourites then think again. Choose herbs and spices over salt, sugar or oil - you can't go wrong!
Don't cut out carbs completelySi says: 'You can have carbohydrates as long as you're careful because your body needs it - carbs just shouldn't be the biggest portion on your plate. It's not rocket science, it's just making sure that the food you eat is comforting, nutritious and is held back on the salts and sugars a bit.'
A fairly prevalent, recent trend has been to cut out the carbs altogether in favour of protein or veggies. For a couple of cheeky chaps who like their spuds, this isn't an option and we understand that feeling too. A rough guide to how big your portion of carbs should be is that they should be a similar size to your fist - yes really!
Keep an eye on caloriesSi says: 'That's how Dave and I lost weight, we counted calories, simple as that.'
Calorie counting is a big part of a lot of diets. Si and Dave's weight loss is testament to how effective this can be when you are trying hard to get your weight under control. Si suggests using foods which have easily identifiable calories in your cooking.
Identify when you're fullSi says: 'Recognise when you're not hungry. I know it's a really simple application but it has to be said. Just go: "Right, before I put this in my mouth, am I hungry?" and ask yourself it really honestly. And if you go 'no', then walk away.'
Although it sounds obvious, we know all too well the pitfalls of over-eating. Just one more mouthful here, a second portion there... but do you really need it? Probably not, so try our Si's tip next time before reaching for more.
Give yourself timeSi says: 'After you've eaten, wait 10 minutes because it gives your body time to go: "Mmm I've actually had enough", which was a big thing for me (when losing weight).'
The problem with eating quickly, if you're anything like us, is that that sometimes you don't realise you're full until it's too late and you've already stuffed down that second portion or heavy dessert.
Work out what suits youSi says: 'It's about your relationship with the food and what you think is going to work best for you, that's all it is. But, there are a few core messages - watch your portions, your carbs, your fats and your sugars. They're the big builders - our bodies store them and they're hard to get rid of because of modern lifestyles.'
No two people are the same, so you have to work what approach is going to work for you as an individual. The main thing is that you find something you can realistically stick to in the long run.
Make small changesSi says: 'I don't have butter on my toast anymore, and I know that Dave doesn't either, it's mad isn't it? I just have Marmite and I really like it.'
Small changes to your diet can have a big effect, it doesn't always have to be a major food overhaul for you to see a difference. From swapping your mayonnaise to a low-fat version to making sure your bacon is lean, there are all sorts of small habits you can tweak to make healthier.
Transform your sweet treatsSi says: 'My top tip to make cakes healthier is to use honey and carrots because they're both sweet. Use some skimmed milk, some ripe bananas, some good eggs and spices and you've got yourself the base for a great cake. Also, you can make fatless sponges, sponges by their very nature have no fat in them when made with egg whites.'
We couldn't help ourselves, we had to ask about baking. Other fruit and vegetables like apples and beetroot can sweeten bakes too.
Get the family involvedSi says: 'If you're making diet food - don't tell the kids, if it's great food, they won't notice. It's important to get kids involved in cooking too - they'll love it, Dave does it with his kids, I do it with my kid. That's how I got my interest in food, at my mum's apron strings. We used to bake bread together and it was brilliant. An inherent interest in food from an early age is a good thing because from that you get an knowledge of food - what's available when, when's the best time to buy stuff. It's all about that passing on of knowledge and skills, which fundamentally is what parents are put on this planet for, I guess.'
Your family might not be wild on the idea of swapping their favourites for low-fat versions as there's always that stigma attached that diet food isn't tasty. It most certainly can be though with a few clever tricks or replacement ingredients.
Be good to yourselfSi says: 'The bottom line is, if you're really trying to lose weight it's important that you really focus on it for a good three, four months and then if you fancy a couple of pints, have a couple of pints, if you fancy an ice cream, have an ice cream. But, it's much easier to do that when you've got your weight under control and you're feeling a bit better about yourself. Carefully watch your fat and oil intake though, a tablespoon of olive oil and a slathering of butter has the exact same calorific value. Try and break your old habits and then give yourself a treat.'
We don't know about you but we certainly crave treats more once we start telling ourselves we can't have them. Extreme dieting usually ends up in an unhealthy yoyo cycle of binging and fasting. Si and Dave approached their weight loss with a healthy attitude which led to great results - it's all about breaking those bad habits.