When their father’s diabetes threatened his life, Ian and Anthony Whitington stepped in with a radical diet and fitness plan. It was a hard slog, but it worked

When their father, Geoff, was diagnosed with type 2 diabetes at the age of 50, brothers Ian and Anthony Whitington were not hugely surprised, and for 10 years, they drifted along and watched from the sidelines.

“Dad had always been the ‘big man’,” says Anthony, 39. “As kids, we thought it was funny. Dad could drink more than anyone, he could eat more than anyone. It was his identity. That’s our dad and that’s what he does.”

“As we got older, of course we worried,” adds Ian, 37. “But everyone around us would say, ‘If he doesn’t want to change, you can’t change him. He has to do it himself.’” So nothing much was done – and Geoff joined the 3.5m adults in the UK who manage their diabetes with ever-greater doses of medication and regular check-ups.

“We were all resigned to our family roles,” says Anthony. “I was a busy financial adviser with four kids of my own. Ian was a busy cameraman with jobs all over the world. Dad was a funny fat guy who drank too much.”

The wake-up calls were different for both of them. For Anthony, it was a family trip to Chessington zoo in 2013. By then, Geoff weighed 127kg (20 stone), had high blood pressure, atrial fibrillation (abnormal heart rhythm), plus everything diabetes could throw at him – a swollen prostate, poor circulation, ulcers on one foot and a bone deformity on the other.

“We were walking around this theme park when the bones collapsed through his foot,” says Anthony. “I remember him grabbing a railing, the blood in his sock, getting him back to the car. Suddenly, this thing that the doctor was managing was very clearly something that wasn’t being managed. Dad was seeing people at the foot clinic who had had a limb removed – and the average lifespan after amputation for a diabetic is two years. We were losing him.”

When Anthony called his brother to say time was running out, Ian needed no convincing.

“The rock bottom for me had been my wedding,” says Ian. “Dad stayed up longer than everyone else – he was always the last one in the room, sitting there with a bottle of brandy. I remember looking at him and it was just horrendous. He was crumpled. He couldn’t get up and dance because of his feet, but he was quite emotional. He said something along the lines of: ‘I’ve done my job. You’re my greatest achievement.’ It was as if that was it. He didn’t need to exist any more.”

In 2014, when Geoff was 62, his sons stepped in with their own special intervention that included a complete lifestyle overhaul, multiple health consultations, family holidays and heart-to-hearts, pacts, promises and pretty much constant rows. Two years later and 45kg (seven stone) lighter, Geoff raced through a 100-mile cycle ride from London to Surrey. He has now been taken off all his diabetes medication as well as his blood pressure pills. He says his sons saved his life – and it’s no exaggeration.

As a professional cameraman, Ian filmed most of the journey, and their documentary, Fixing Dad, aired on BBC2 last summer. Anthony’s wife, Jen, a fitness trainer, co-produced the film. There’s also an app for those wishing to do the same, and a book, written by Jen, that includes a meal and exercise programme, plus advice on the mental leaps needed to fix a stubborn family member. The “fixing” terminology couldn’t be more apt for a man like Geoff – who has spent most of his life fixing things for others.

“Everyone described Dad as ‘generous to a fault’,” says Anthony. “He’d pay the parking fines of complete strangers. As kids, we saw him stop the car in the street to chase after muggers. I remember when my wife, Jen, was having a bad day after our first child was born. I was at work so she phoned my dad. We were living in Surrey at the time and Dad said: ‘I’ll come over now. Is there anything you need?’ It turned out he was 100 miles away, but he told Jen he was just down the road.”

“We owed Dad a lot,” Ian agrees. The boys had grown up in Bromley and their parents divorced when they were eight and 10 years old. “It changed the dynamic massively. We were with Mum in the week and Dad at the weekend – and we got into this pattern of Dad not being able to do enough for us. We didn’t miss holidays that richer kids were going on because Dad put it on a credit card. If we wanted to do something, he let us. He was spoiling us, really, and by the time we were adults, his debts were so bad, he was a BT engineer in the day and working nights on the Underground and as a security guard. We felt a lot of guilt about that.”

So why was Geoff so good at looking after others, but hopeless looking after himself? Perhaps, with busy, grown children, he felt a bit redundant. “I think I’d reached the point in my life where my children were happy, they had their jobs, they were OK. I’d worked all my life, I’d done my job and I wasn’t needed,” says Geoff, who has been married to Marilyn, the boy’s stepmother, for 20 years.

“My wife was going to be the one to suffer if anything did happen to me, but I suppose I didn’t give it much thought. My life involved working very long hours, which meant a lot of driving around, and a lot of stopping and eating.” (His sons claim Geoff couldn’t pass a McDonald’s without pulling in, and there was always a can of Coke rolling round the floor of his van.)

So what made him agree to this project? Was it to save himself or to please his sons? “I suppose a little bit of both,” he says. “I certainly didn’t think it could help or change anything – I didn’t know anyone who had reversed diabetes. As far as the filming part was concerned, I ignored it, as that was never going to make it on to the TV. It was another of their little projects that was never going to go anywhere! But they asked me to go along with it for a period of time, like a contract, and I agreed.”

They kicked off with a roadtrip to the Pyrenees. “Dad’s surroundings weren’t helping him, so we wanted to get him away from his takeaways, his TV dinners and fridge full of cellophane,” says Anthony. “The old, fun Dad was disappearing, and we wanted to find that sense of adventure. We got him cooking, cycling, tombstoning. I’m not sure jumping into ice-cold water in the Pyrenees in February is the best thing for someone with atrial fibrillation, but I’ve never seen him as elated as when he got out of that plunge pool.”

While they were away, they talked about Geoff’s mother – a shop worker who would do anything for anyone, and who died from septicemia at 69, when her stomach ulcers went undetected.

“It needn’t have happened and that upsets me more than anything else. I didn’t want my sons to feel like that about me,” says Geoff. On the last night, they went through photo albums and looked at old family pictures, as well as pictures of his grandchildren. “We said: ‘This is all about your family, who don’t want you to be dead in two years,’” says Anthony. “We made a pact and Dad promised to commit to this – we made him swear on the only book he has ever read – Shadow the Sheepdog.”

Back in the UK, the brothers dug out Geoff’s bike and got him back on it – at first with Anthony running behind pushing him up the hills. “After just three weeks, he was at his foot clinic and they said, ‘My God, we’re not having to scrape the ulcers as much. The bloodflow is there – what have you been doing?’,” says Anthony. “That gave Dad hope. It kept him going.”

Discovering a very low-calorie diet that was having some success in reversing diabetes was another breakthrough. The Diabetes UK-funded study by Professor Roy Taylor at Newcastle University put patients on an eight-weeks 800 calories per day diet. This was followed by a long-term, low-carb regime, as close monitoring of Geoff’s blood sugar levels showed that carbs were causing significant spikes.

It wasn’t easy. There were a lot of rows. “We were turning our relationship on its head and it got to the part where we were very obviously being the parents and Dad resisted that,” says Anthony.

“It almost felt like bullying at times, with both of them firing at me together,” agrees Geoff. A typical example is early on when the two were coming to Geoff’s so he bought a Chinese takeaway. “It was a treat and I’d tried to pick foods that were ‘compliant’,” says Geoff.

“But he’d bought enough for 20 people,” says Ian. “The whole table was covered and so we had a go at him. He wouldn’t talk to us for two days!”

This, says Ian, is why families are in a stronger position than health professionals. “The way you eat is incredibly emotional and if you criticise somebody around food, you can upset them very quickly. You need to get over that a bit. Families can cross the line and go where professionals are never going to be able to go. We could say things that a doctor could never dream of saying. You can’t be nicey-nicey all the time. You’ve got to challenge each other. Something we’d say to anybody is don’t be afraid of that conflict.”

When we meet, they are still bickering over a toffee bonbon that Geoff had eaten the previous day while babysitting for Ava, Anthony’s seven-year-old daughter. (Ava had a bag full of them.) Ava promptly told her dad. A series of angry messages were exchanged, with Geoff telling Anthony to find another babysitter. (“He’s not the finished article,” sighs Anthony. “But he’s in reverse gear.”)

Despite the odd slip, everyone appears to be glowing with good health. Anthony and Ian also lost 32kg (five stone) between them – they didn’t ask Geoff to do anything they couldn’t do themselves – while Marilyn has lost 19kg (three stone). The couple cycle together, cook together, and they have ditched the takeaways and TV dinners. “We sit at the table and eat now and we talk about food,” says Geoff. “We really enjoy it.”

With the new book out, the father-and-son team are about to mentor four new families through a similar health overhaul, and are travelling the world as speakers at medical conferences. Anthony has resigned from his career in finance and Geoff has been able to say goodbye to his punishing night shifts.

And in between this, Geoff is back fixing things again. “I just renovated Ian’s shed, rebuilt the roof and I did Anthony’s garage, too. I’ve put shelves up for him. Before all this, I couldn’t have got on a ladder. It has been the best three years of my life – and I just feel terrific.”

• Fixing Dad by Jen Whitington (Short Books), £8.99. To order a copy for £7.64, go to bookshop.theguardian.com or call the Guardian Bookshop on 0330 333 6846. Free UK p&p over £10, online orders only. Phone orders min. p&p of £1.99.

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