Few British sportsmen are affected by the rigours of adhering to the fasting period of Ramadan quite like former two-weight world champion boxer Amir Khan. The 28-year-old has among the most attuned physiques in world sport. It might be destructive and powerful in the ring but it is fragile and vulnerable when devoid of fuel.
During a 30-day period starting on 18 June, Khan will abstain from eating and drinking during daylight hours and begin a period that will shred his body of muscle and make training to a high intensity a near impossibility.
"Fasting makes you feel weak," Khan said. "You have to wake up at four or five in the morning to eat, but you're knackered and you don't feel like food, you have to force it down. I wouldn't fast on the day of a fight, though."
The dates of Ramadan change every year and are worked out based on astronomical calculations. Previous years have seen the timing of fasting derail Khan's training regime and see him forced to abandon offers to fight some of the biggest boxers in the sport.
In 2015, the period has been dragged forward meaning Khan has eight-and-a-half weeks to prepare for a possible meeting with unbeaten American welterweight Floyd Mayweather Jr, which could take place on 12 September.
One of the core values of Ramadan is to consider others, such as the poor. Khan will therefore devote much of his time to his charitable foundation, which attempts to empower disadvantaged young people and support emergency disasters. Boxing will be far from his mind.
For some, the burden of competition and success means their religion takes an untimely back seat.
During the London 2012 Olympic Games, Briton Mo Farah gave up Ramadan, which ran throughout the showcase event as he prepared to go for 10,000m and 5,000m gold. The Somalian-born runner would go on to clinch the long-distance double and undertake a period of abstinence later in the year.
While it might appear to hinder and constrict many sports people, there is a group who are inspired rather than hampered. The fulcrum of the cricket season for England all-rounder Moeen Ali runs through the period but instead of allowing it to dictate his performance, he takes inspiration from his faith.
"I think if I was in an office I would find it harder, to be honest with you," he explained. "Because you're probably used to snacking but when I'm playing cricket it keeps me busy. I'm out in the field.
"I just got used to it. It's something that keeps me stronger. I actually score more runs and I do better. Probably because I'm more focused."
The first of the Ashes Tests in Cardiff takes place during the final week of fasting and could yet be England's secret weapon against Australia.