Everything changed overnight. I said ‘no’ to hamburgers and fries, which I had previously welcomed with open arms (or more accurately, an open mouth). Pizza was out and broccoli was in. Soon I was running four miles daily, and I even visited the gym for more than conversation. Forty pounds gradually melted away.

I actually overdid it a little – that’s my tendency. I knew I had started looking a little gaunt because strangers would offer me food and friends asked me how long I’d been ill. For seven beautiful years I kept it up, and I even fell into the sin that so easily entangles the feet of the healthy: I started to look down on others who were chunkier and out of condition. I lost fat, but gained the flabby haughtiness of a superior attitude.

But in recent years, I slacked off. My backsliding was gradual, so relatively unnoticeable. I fell for the seduction of sticky, fat-laden puddings. What had been an exercise regime became an occasional pastime, and my running shoes grew pale because they saw so little sun. A little cheese here, a cheeseburger there, and before I knew it I was heading back into the obese zone.

That’s exactly what can happen to faith. It can suffer gradual, slow, imperceptible erosion. People don’t suddenly lose their faith – although that does happen, especially when pointless tragedy strikes – but often they just mislay it, and then can’t for the life of them think where it’s gone. Instead, we drift; lulled into believing that cruise control works for believing, which it doesn’t.

Recently, much has been made of the announcement from Bart Campolo (son of Tony) that he has abandoned faith and become a humanist chaplain. Tragically, a few Internet heresy hunters licked their lips with delight. How sad their smugness is.

Others have written more compassionately about Bart’s exposure to the terrible pain of inner-city ministry, and his lonely wrestling with doctrines that, to him, became implausible. I was impacted by his candid confession that his faith ‘died the death of a thousand nicks and cuts’. Ever so slowly, this bright, brave warrior was worn down. Faith drained from him, drip by drip, until the tank was finally empty.

I pray that Bart will once again be overwhelmed by the authentic love of the living Christ, and that you and I will intentionality guard and nurture our own faith.

Just like a diet or exercise programme, faith must be recommitted to daily. Without that diligence, believing can turn into a dull, grey habit, and churchgoing and all the accompanying Christian stuff can start to look flaccid and unattractive. Ironically, that’s when we really need the Church so that we can huddle together and affirm the truths we believe.

So today I will pray rather than just vaguely believing in the power of prayer. For decades I had decried the ‘quiet time’ as legalistic oppression, and I became a pauper as a result. I’ve changed my mind on that. And faith demands that I will hang in there when God is unnervingly quiet, especially when he seems extremely chatty with others.

I’m glad to report that I’m back on track with the fitness programme and healthy diet. The surplus pounds have gone again. I’m even wearing an electronic band to monitor my daily exercise and calorie intake.

And, while I’m at it, I’ve decided to follow Jesus. Today.

By the grace of God, no turning back.

No turning back.