I can hear myself turning into a jerk. It can be quite an out-of-body experience.

Something remotely fitness or health related is mentioned in conversation, and my tuppence worth will involve a “healthier” option. I’m even starting to annoy myself. I wasn’t always like this. And I don’t like it.

Something happens to those who convert. They become slowly, but steadily, intolerant of non-believers. And, worse, they want to share the good news with everyone.

Have you heard? Exercise is good for you. Eating crap isn’t.

Who knew?

My wife smokes. I used to. Now I smugly pass on the latest lung cancer figures; I wonder aloud every time a bill comes through the door about how we might reduce spending; I moan about being left to mind the drinks while the smokers go to meet new friends outside the pub door. Have I fake coughed? You know I have.

Now, though, I’ve found another religion to be a zealot and a git about. And I’ve taken to it like a health freak to celery. It’s maddening, because I used to be a card-carrying member of the other group – the one who scoffed at those who preach from the bible of health and fitness.

We all know them – people who feel better about their own achievements knowing they’ve made someone else feel bad about it.

Guilty conscience

Social media, in particular, is a constantly refreshed guilty conscience. My former routine involved a snack while checking Facebook, which usually meant eating a KitKat while reading about a "friend" feeling "awesome" after a "two-hour cardio workout". I'd resolve to give them the finger (if they were within throwing distance of my KitKat).

Perhaps a little info really is a dangerous thing. Now that we are eating slightly healthier than a few months ago, we can talk with an authoritative tone (though without the requisitive knowledge) about how essential fatty acids are required for the biological process but not for fuel for the body.

Can you tell the number of calories in whatever your friend or colleague is eating? More importantly, can you keep the number to yourself?

There is, of course, a chasm between health and fitness evangelists – who are rightly proud of their own achievements and want to encourage others – and those who feel their new-found loss of a spare tyre has also unburdened themselves of any need to be sensitive to others.

People are perfectly entitled to boast about finishing a 5km/10km/half- marathon/crazy-distance-no-one- should-put-themselves-through. However, surely you cannot shame someone into adopting healthy habits? And, ironically, it reveals a person’s ugly side.

A friend once inspected my (admittedly high-carb) plate and commented that they’d never eat a lunch like that, because “they love themselves too much”. Luckily for them, I was too lazy to fetch a second fork, so I confined mine to my wedges.

High on my social media feed at the moment is a line from a health “enthusiast” which encourages “fatties” to get off the couch “and feel the burn”. If part of your identity is feeling fitter and healthier than others, well, then jog on.

It’s time to get down off your pedestal (remember to stretch first).

I’m now exactly two stone lighter than I was in March, though if I continue to lecture others then perhaps the only thing I’ll have lost is five months.

Step by step
- Intellectual approach to losing weight
- Most apps on straps are rubbish
- My daughter is trying to kill me
- It's not you, it's me. Hold on, it's you
- You don't have to turn into an ass
- I met my next child's godfather at a race
- It's tough when momentum runs out
- No sweetness, and lite everything
- Stopping the treadmill with your tummy
- When it's my turn to make dinner . . .
- The kitchen table looks out for us
- Skinny friend eats like an elephant
- Tomorrow we diet
- How to get back into exercise
- At what age do you fall apart?
- I'd jog for wine
- I'm a binge drinker
- What if losing weight makes you sad?
- 12 months later, time for health tips
- The ultimate global deception