We've all been on a diet at some time or other with many people lurching from one weight-loss programme to another without much long-term success. However, a recent trend for intermittent fasting seems to be gaining traction and proving to be a hit with both dieters and health experts.
The 'caveman diet' which involves going for long periods of time without eating and then consuming as many calories as needed, appears to be hugely beneficial for both weight-loss and overall good health.
Researchers at the University of Graz in Austria monitored participants who ate no food for 36 hours and then consumed whatever they wanted for 12 hours. All of the participants lost over seven pounds in four weeks. And although cutting out food for such a long period of time may seem dramatic, none of the participants suffered ill health.
Personal trainer Marc Smith (47) of Complete Fitness has been fasting intermittently for the past year and says he has lost weight and feels in great shape physically.
"I did a lot of research into different diets and while many seemed to be a fad, I liked the idea of fasting as the science behind it made sense to me," says the Dubliner. "I started about a year ago with eight hours of fasting and gradually took it up to 16 hours. I will do it for five to six days within a six-week period and then will eat normally for three weeks before starting the whole process again.
"I have found it quite easy to do as it just involves me not eating anything after an early dinner in the evening until lunchtime the following day. As well as the benefits for weight-loss I also believe it re-sets my gut and gives me more energy - and this works well when I am doing endurance sports as I can go for a lot longer without needing to eat."
Sean Fanning (36) has also been fasting for the past 10 months and says he has lost "a huge amount of weight".
"I have been trying to lose three stone for a few years," says the marketing executive. "I joined the gym and tried all sorts of diets but it just wasn't happening for me because when I worked out, I would feel so hungry afterwards that I probably ate more calories than what I had burned at the gym. Then the diets I went on were fine for a while but I couldn't sustain any of them as it was too difficult to be trying to count calories all the time.
"So a friend told me about this fasting thing and said if I started off easy by just eating nothing after 8pm and then not having breakfast until mid-morning I would start to lose a few pounds. It wasn't difficult at all so I started going for longer and now I do three days a week, twice a month where I have a really big lunch and then a lighter meal at around 5pm and nothing at all until lunch the following day.
"Once or twice I have done it until dinner the following day and that is a lot harder, but it really works and now that I'm in the routine, I don't mind it at all - I fast for six days in the month and have almost reached my target weight loss. I don't know how long I'll keep it up for but it's good to know that if I start piling on the pounds again, there is a way to get rid of it quite easily."
While studies have shown that not eating for prolonged periods can result in malnutrition, intermittent fasting has not been shown to have any long-lasting ill effects.
Composer and author Elaine Nolan (47) - who is soon to publish her latest thriller, Rule 53 - has been doing what is known as the 16-8 diet for the past year. This involves not eating for 16 hours and then having an eight-hour period to consume all her food for the day.
She says that it has not only helped her to lose weight but has also boosted her energy levels and creativity.
"I finish eating at 6pm every day and don't eat anything until 10am the following day," says the Carlow woman who works as a civil servant by day. "I have tried many diets before and found them very difficult to follow but this one is great, particularly as I have an app on my phone which keeps me on the straight and narrow.
"I decided to do it because I'm in the early stages of perimenopause and I stress-eat and stress-drink so I needed a reason to be disciplined as otherwise every evening I would just consume whatever I felt like and at this stage of life, it's very easy to put weight on. But within two weeks of fasting I could really see a difference - I had lost weight, was more alert and I've also found that I have more energy, drive and creativity which is really important because after dealing with the public for eight hours, I need to have a clear mind if I'm going to write anything in the evening."
According to research, during intermittent fasting, the periods when you are not eating give the body time to lower insulin levels, which reverses the fat-storing process and when insulin levels drop, the process goes in reverse and you lose fat.
But it isn't just for people who want to lose weight, as Niamh O'Connor discovered.
The 46-year-old artist has suffered with an autoimmune disease for her whole adult life and says she has tried every possible treatment to alleviate the symptoms and it wasn't until she addressed firstly what she was eating and then when she was eating it, that she noticed a marked difference in her health.
"I have had problems for years with autoimmune disease and in 2016 I developed fibromyalgia and chronic fatigue," says the Monaghan woman. "It would come and go in very bad flares and I tried everything that the medicine world had to offer but nothing seemed to work.
"I gave up drinking and gluten and went down the natural medicine route but it was only when I was looking into treatment for my brother who has ME that we came across a doctor in the UK who specialises in the PK diet (Paleo Keto) that I started looking more at the food side of things.
"This diet involves no grain, sugar or dairy and is high fat, low carb and moderate protein. Once that began to make a difference I started looking a little bit further and discovered a man called Ken Barry who promotes intermittent fasting. I was curious so decided to give it a go and it has made a massive difference to my life.
"I do a variation of the 16-8 diet and try not to eat between 8.30pm and lunchtime the following day for three weeks a month. If I'm hungry in the evening or first thing in the morning, I'll have black coffee with butter in it as it doesn't interfere with the PK diet. But it's very doable and has really improved my standard of living."
Marc Smith agrees and says he cannot see any reason for not fasting every now and then.
"I have done quite a bit of research into it and everything I have read is all good - at least there is nothing to say that people shouldn't do it," he says.
"So if anyone is thinking of giving it a go, I would advise them to start slowly with perhaps not eating anything after 7pm until 8am the next day and then work it up to whatever level they are comfortable with - but if people are exercising during this time, they must make sure to supplement properly and have sufficient energy boosts."
As a glamorous former fashion model, close friend of the Royal Family, and nutritionist to a host of A-list celebrities, it would be easy to assume Gabriela Peacock extols the kind of quirky dietary practices so beloved of the rich and famous - seven-day juice cleanses, bland broccoli breakfasts, soul-sapping zero-carb regimes.