With 40 days to go now I was always planning to do a column on nutrition in my run-up to the marathon.

This is the ideal week, in a perverse way. Because I haven't been able to eat - for 4 days.

Last week after my long run, I contracted food poisoning. I can only narrow it down to a pack of blueberries that must have had a bug on them. I put them on my breakfast porridge, which was the last meal I ate until the start of this week. Let's not put you off your tea by describing my suffering and symptoms, but suffice to say the illness was unpleasant and even painful, though it hastened the weight loss by about three-quarters of a stone, temporarily at least.

But I am now more or less recovered. I will continue to actively manage my intake of food, essential for the race preparation, but also, for me as for all of us, a crucial element in maintaining good health.

Obesity is known now to be terribly unhealthy, and epidemic in Scotland. It is something that no-one wants, and causes suffering - certainly physically, as it makes heart attacks much more likely - but also psychologically and socially, sufferers are conscious of their image and no doubt uncomfortable heaviness as they go through daily life.

It may now sound glib for me to say that overweight people are responsible for their own health and destiny. I do say that, but I absolutely understand the context that sufferers find themselves in. On the one hand, the comfort-eating and self-reward seem almost justified in a hard world, and on the other, it is so easy to let grease, sugar, alcohol, carbs and fat all slip down for instant gratification.

As I regularly say, I am not a health expert, certainly not a nutritionist or dietitian. But I am a middle-aged man with a penchant for putting on weight. In a consequence-free world you wouldn't see me for chips, burgers, beer and pizza. But what I have done, as many have done before and better, is to take the first steps to active diet management rather than passive grazing.

I could wax lyrical and extend the analysis to other areas, work, business, relationships - the more you are in control, the better you can direct your own life.

Life isn't easy. There are pressures and stresses, and being aware of calories or the balance of food intake is not an obvious priority when you face bigger issues, but you are what you eat.

It's a well-known saying, all the more true for being traditional. A less familiar quote, but one you've seen in these columns from time to time, is by my old mentor, Doctor McCoy of Star Trek "All you need for living longer is to eat right and get plenty exercise". And even though strictly speaking he won't actually use these words for another 300 years (ok, he's not real, he won't ever use them), they are true.

Eat right. That is the most simple thing. Plain food, home cooked, natural fresh ingredients, moderation in the extremes of sweet and savoury. A banana is healthier than a muffin. Jacket potatoes are better for you than chips. Roast ham is better than a sausage roll. Wholemeal bread is more nutritious than industrial white.

There are lots of these simple comparisons, and if you shop judiciously, you can eat healthy food just as cheaply as you can inject rubbish with fat and sugar into yourself.

So what do I eat? Breakfast is either the superfood porridge, with or without fruit chucked in, bran flakes or a kipper, with fresh fruit juice. No toast for the moment.

Lunch is fruit, a few almonds and a couple of dry oatcakes. Dinner is home-cooked fresh meat/fish with veg or salad. No dessert. Lots of water.

Some nights I do allow myself a glass of wine. But no beer. During the day in the office I have a couple of cups of black, properly-brewed coffee - no sugar. One thing I don't have is a sweet tooth, but if I did I would be swearing off biscuits and suchlike, though I do eat a small amount of dark chocolate especially after a run.

So don't just stuff your face. Treat eating as a pleasure by all means, but as an important bit of personal business and a way of enhancing your life, not risking it.

Bon appetite.

Remember my charity page for the hospice movement, www.justgiving.com/AustinLafferty