Everyone loves a bargain, as those restaurant chains which offer you special "all you can eat" deals for a fixed price know all too well. In Pakistan a pizza company had been doing a roaring trade during the Muslim month of fasting. Families who were ravenous after a day of not eating would pile into the restaurants for the evening meal of Iftar to eat pizza after pizza for as little as £7. But now there's been a national outcry over the cutting of this special deal. The pizza chain says stuffing yourself with endless food goes against the spirit of Ramadan and is an invitation to gluttony. Gluttony's not about eating considerable amounts but eating just for the sake of it. Olympic athletes like Mo Farah and Bradley Wiggins consume huge amounts of protein and carbohydrates at particular times as part of their preparation for races. The food has a purpose. They control it, it doesn't control them. Gluttony is the exact opposite, which is why Christianity describes it as a deadly sin, an occasion when we let our desires be so sated that they shape us, both physically and spiritually. With fasting, many religions use it as a discipline of the body, as a sacrifice for God. And yet fasting is also beneficial to our health, as a Horizon documentary this week explained. Medical evidence shows that not eating a couple of days a week can boost the brain and aid longevity, something that's apparently due to how we evolved. That makes me wonder if the ancient peoples of the desert where the Abrahamic religions of Judaism, Christianity and Islam originated had somehow realised this. But what they certainly advocated is that just as exercise is good for the body, so fasting is a spiritual exercise, allowing us to flex the muscles of the soul. They believed that if we limit what we eat, particularly on special days or seasons, it helps us focus on God, putting love of him before our love of things, before our earthly desires, before ourselves. The Gospels record Jesus' 40 day fast in the desert had him tempted again and again by the Devil. It was a testing of his humility. That is why in the Christian tradition fasting goes hand in hand with prayer and the giving of alms to help those less fortunate than ourselves. It is a moment to focus on what is truly important, or to use current sporting jargon, get in the zone. Giving up food for the spiritual athlete can do the same job as targeted eating for a sporting hero as he prepares for the race of their life.