I'VE A theory about why the nation is so fat.

It's because of Indian restaurants. Well, them and some others.

When I was young, our family dined in restaurants a total of zero times. There was a wedding dinner once that I recall and a sit-in at a fish and chip shop in, I think, Kirkcaldy. But that was it.

Meals at home were decent but rarely large: two slices of luncheon meat, two potatoes and a salad of baked beans (one tin between four). So when I arrived at man's estate and was taken to an Indian restaurant for the first time by student friends I was flabbergasted.

I looked at the plate and thought: "I can't eat all that." And I don't think I ever have, certainly not if preceded by a starter.

All that rice, all these lumps of stuff, all that sauce. It's huge! It's what the Indians think Westerners want and, to be fair, it is what Westerners want. Other restaurants are nearly as bad: huge portions.

At the other extreme, we don't want ripped off by what was once nouvelle cuisine, a passing fad that typically consisted of one asparagus tip and a slice of something posh like corned beef.

When I started dining out, I thought the big portions were what everyone else had been eating all along and so I started having them myself at home. I put on three stones and thought my moobs were pecs.

In restaurants folk feel obliged to clear their plate lest the chef think he's done something wrong. But there's an answer to this conundrum: doggy bags. These let you off without stuffing yourself to Bloatland and beyond, while telling the chef you enjoyed his meal so much you're going to have it for breakfast too.

A pilot scheme encouraging the practice has been so successful it's to be rolled out the length and breadth of Scotia Minor.

Zero Waste Scotland's Good To Go trial, involving 16 restaurants in Glasgow, Edinburgh, Irvine and East Kilbride, saw "dramatic reductions" in food being binned, with 92 per cent of diners who took food home eating it later.

Apparently, one in every two punters is too embarrassed to ask for a doggy bag. But, once it becomes a social norm, that should pass. All human life is an embarrassment. Don't worry about it.

The amount of food wasted in restaurants is staggering: in Scotia alone, an estimated equivalent of 800,000 full meals go in the bin every year. That isn't acceptable in the food bank era.

Don't leave food on your plates, folks. Get it bagged. Unless it's luncheon meat. In which case, bin it.