Abdul Buhari has been fasting for Ramadan since the age of 12, but this year he will be missing the holy month. He has good reason for it: Buhari, 30, is one of the UK's top discus throwers and will be representing Team GB in the men's discus event at London 2012. He has decided not to risk his Olympic performance by being without food or water.

"It was a really difficult decision because I've fasted all my life for Ramadan – it's incredibly important to me. But if I fast, it will be impossible to stay in peak condition and perform at my highest level in the Games," he says. "I believe God is forgiving, and I'll make up for every single day I've missed." He plans to fast later on in the year.

This is the second time Buhari has missed Ramadan; last year, when it coincided with the athletic world championships in Korea, was the first. After much discussion with his coach, wife and several imams, he concluded that fasting and competing in top-level athletics just weren't compatible. "I went through it with my trainer, looking at whether I could get enough calories for the nutrition and energy I needed, but in the end we decided it would be too risky."

In Korea, Buhari shared a flat with fellow Team GB athlete and Muslim Mo Farah for the championships. "We both weren't fasting and we found that really hard. No Muslim wants to miss Ramadan."

All four of Team GB's Muslim athletes (Buhari, Farah, rower Moe Sbihi and fencer Husayn Rosowsky) have decided not to fast during Ramadan this year, so as not to jeopardise their Olympic performance. While Farah and Rosowsky will also make up for it later in the year, Sbihi has instead decided to provide 60 meals a day for the poor for every day of fasting he misses. He came up with the charitable solution after consulting with Muslim scholars in Morocco, where his father is from.

More than 3,000 Muslim athletes are expected to participate in London 2012, although the games organisers say it's impossible to know how many are fasting. Still, they are prepared: fasting athletes can order "breaking-fast packs", filled with dates, water and energy bars, and the canteen will be open 24 hours so anyone fasting can eat sehri, the pre-fast meal consumed just before sunrise, in the early hours.

But is it really advisable for athletes to compete or train while fasting? In 2009, the International Olympic Committee (IOC)'s nutrition working group began investigating the impact of fasting on sports performance. A team of scientists, led by Ron Maughan, professor of sport and exercise nutrition at Loughborough University, analysed more than 400 articles on Ramadan and sports, and published its findings in the British Journal of Sports Medicine last month. The report concluded: "Fasting of short duration or intermittent nature has little or no effect on the health or performance of most athletes … Ramadan observance has only limited adverse consequences for either training or competitive performance."

"Everyone tends to assume that performance is going to be affected by Ramadan, but there's nothing unusual about playing sports in Ramadan," says Maughan. "Most people who fast for Ramadan, whether they are athletes or not, have been fasting for years. They know how to cope and how far their bodies can go. So it's perfectly safe."

Even though they have opted out of this summer's fasting, Buhari, Sbihi and Rosowsky have all trained during Ramadan in the winter months without problems. As Rosowsky puts it: "You just focus, man up and get on with it."

Buhari weighs 20 stone. He eats six meals and drinks six litres of water on a normal day. On training days during Ramadan he would wake up extra early for sehri, eat a large variety of slow-releasing carbohydrates from porridge and seeded bread to sweet potatoes, brown rice and pasta, along with plenty of water and electrolytes to prevent cramping. At the end of the fast, he'd repeat the process. "Sure, sometimes I would feel thirsty, but ultimately my faith was my motivation. I could draw on that to get me through," he says.

Being able to train during Ramadan is one thing for a competitive athlete and another for your average person, warns Drew Price, a performance nutritionist who works with athletes and Premiership footballers who observe the Ramadan fast. "Ramadan isn't as difficult as people think for athletes, but they have a whole support team to monitor them while fasting. The average person won't have that, so if they want to exercise and fast, they should listen to their bodies. Generally, the fitter you are, the easier it is. Ramadan is only a few weeks out of the year, so you can afford to take it easy in terms of the intensity and volume of exercise you do for one month if you train well the rest of the year."

Personal trainer Imran Ilahi owns a health club in St John's Wood, north London, and last year published Fit4Ramadan, an online fitness manual about how to stay in shape while fasting. He works out during Ramadan, preferring to train before sehri, rather than during fasting hours.

"The key is to focus on maintaining your fitness during Ramadan, rather than improving it or making it worse," he says. "You can still eExercise before you start the fast, or after you've broken it. Just do slightly less than you normally would and you'll find it gives you more energy."

Asif Ahmad, a 26-year-old from London who goes to the gym three times a week during Ramadan, agrees. "It's a strange concept to comprehend, but playing sports really does mean that adrenaline overshadows most of your natural reactions such as thirst or fatigue," he says "It's all about discipline, after all."