Spencer Matthews showed off her very ripped physique as he posed for a shirtless Instagram photo while in the gym on Sunday.

The former Made In Chelsea star, 36, displayed his chiselled abs as he tensed his muscles during the workout and admitted this is the ‘best shape’ he has been in.

Spencer revealed the ‘five changes’ he has made to his lifestyle that have made the ‘biggest difference to his physical and mental wellbeing’.

The TV personality – who completed 30 desert marathons in 30 days – put his new physique down to clean eating, weight training, cardio, fasting and avoiding alcohol.

He wrote: ’36 years old. Fittest I’ve ever been and in the best shape of my life. Here are 5 changes that have made the biggest difference to my physique and overall wellbeing.

‘1. Eating clean unprocessed food. I try to make sure that where possible I eat fresh, single-ingredient food. Lots of steak, eggs, rice, vegetables, fruit, nuts and yogurt.

‘2. Regular strength training. Lifting weights at least three times a week for an hour at a time has become not only a necessary part of my routine but something that I would struggle to live without.

‘3. Cardio… Running / cycling. Adding regular cardio to my training has completely changed my athletic ability and mental state. The more time you give to this the more your life will change for the better. Get out there and move… You don’t become old then immobile, you become immobile then get old.

‘4. Avoiding / Limiting alcohol. I only drink very occasionally and even then I wonder what the point is? I’m long past finding it “fun” and there is no benefit to it whatsoever. There are many great products out there that can replace alcohol if you get the urge to drink. @cleanco is a good place to start.

‘5. Fasting. I generally won’t eat anything before 12-1pm. I’m not particularly rigorous with this but tend to only eat when I’m hungry. We do not need anything like three meals a day.’

It comes after Spencer set himself a brand-new World Record Challenge – seven full Ironman Triathlons in seven continents.

The broadcaster is aiming to top his historic 30 desert marathons in 30 days, three months after he ran 786 miles on sand in the Jordanian desert, raising almost £600,000 for Global’s Make Some Noise appeal.

For his next mission, the father-of-three will attempt seven Ironman Triathlons in seven continents, as quickly as physically possible.

Each triathlon will see Spencer complete a 3.8km swim, 180km bike ride and a full 42.2km marathon in each of the seven continents, finishing with the hardest one of them all, in Antarctica.

Spencer, who’s married to TV presenter Vogue Williams, 39, is aiming to achieve his hardest challenge yet in under four weeks while the only person to ever accomplish this in history, did it in four years.

Spencer said: ‘This is without a doubt, the most mentally draining, physically demanding, and most dangerous challenge I’ve ever undertaken and will push me to my breaking point.

‘Running 30 consecutive marathons earlier this year opened my eyes to what the human mind and body is capable of.

‘Despite the gruelling conditions, I fell even more in love with running. As soon as I crossed the finish line, I was itching for the next challenge.

‘This is without doubt ambitious – but what I have discovered is a love of pushing myself, and of achieving what would have previously been unachievable to me.’

If successful, Spencer, who’s a father to Theodore, six, Gigi, four, and Otto, two, will hold the Guinness World Record for completing a 140.6-mile triathlon distance on seven continents for a male.

As Spencer attempts to conquer the seven full Ironman Triathlons in seven continents, he will be filmed by a TV crew from production company Whisper, as they capture his epic journey for a new documentary series.

He added: ‘I know that I’ve bitten off a lot here but the countdown starts now and I’m thrilled to be working with the team at Whisper to capture every second of what I hope viewers will find to be an exhilarating journey.’

To prepare for the ‘Seven in Seven’ Spencer will undertake two new sports, both swimming and cycling which he has very limited experience in.

Spencer spoke to Chris Evans during his Virgin Radio Breakfast Show, saying the Ironman Triathlons will push him to his absolute limit.

He said: ‘I wanted to try and do something bigger and exciting on a global scale. It’s going to be pretty rough…

‘Initially I wanted to start with Antarctica to get it out of the way and then realised it might be a depressing thing not to finish.

‘It’s quite a complicated thing, temperatures are below zero, there’s a swim in 0.2 degree water… We have a lot of work to do, a lot of preparation.’

Spencer explained he will begin in South Africa before moving onto Australia, Asia and Europe, eventually flying to North and South America, before concluding his journey in Antarctica.

He added: ‘We are going to aim to do it in under four weeks. I believe we could do it in around two weeks. But Antarctica is quite like Mount Everest in many ways because the altitude can change.’

Spencer reflected on having an ‘epiphany’ during his 30 under 30 marathon challenge in August.

He said: ‘I was deeply touched by the affect that it appeared to have on others outside of the fundraiser.

‘I learned that normal people can do extraordinary things. A lot of interesting life lessons were embedded in that challenge.’

During his appearance on the Breakfast Show, Spencer admitted to wishing he could reverse some of his behaviour on Made In Chelsea, after joining the E4 series in 2011.

Spencer, who’s previously spoken about his deep shame with alcoholism, said: ‘I never felt like a complete person doing that show.’

He added: ‘I look back a lot of my life with regret and shame and this Word Record we just achieved changed my life completely. I felt really proud of myself. My life is becoming more purposeful and I’m delighted.’