I'm looking at a two-litre bottle of Coca-Cola.

It cost £1.99 but the label tempts me to buy two for only £3 – so why not? Well here's a reason. The nutritional information on the side says the bottle contains no protein, no fat, no fibre and no salt but 26.5 grams of sugar for each 250ml serving. It is a 2000ml bottle. That makes the total sugar content 212grams – almost one-quarter of one kilo or half a pound.

The £3 deal would contain an entire pound of sugar. That is the only nutritional value in the bottle. Yet how many people who guzzle fizzy drinks in place of water would knowingly sit down with a bag of sugar and scoff the lot?

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Not many, since we know sugar is bad for us: it's addictive and can cause cancer, diabetes and heart disease.

For too many people drinking fizzy drinks is a dangerous habit. Is it time to make it more expensive?

The road to obesity is paved with good intentions and becoming ever more crowded. The problem is so large (if you'll excuse the pun) it is costing the NHS £5.1 billion a year in the UK and becoming worse year by year.

It is reckoned that by 2050, 60% of men, 50% of women and 25% of children will be obese. I can't think of a more efficient way of making a country utterly miserable as well as profoundly unhealthy.

The prospect is unaffordable in every way. So should we fight the 20% tax on fizzy drinks proposed by the Academy of Medical Royal Colleges or welcome it?

It has to be the latter. We know what makes us fat. We've been warned about the detrimental effects of a diet full of sugar on our bodies, on the economy – and on the national aesthetic. Yet when a branch of Krispy Kreme doughnuts opened on the outskirts of Edinburgh last week, a queue formed.

We're sugar junkies – so if willpower won't shift our habit, a financial penalty must be worth trying. At least a tax will help to pay for some of the huge medical costs.

It is one of 10 action points which together sound authoritarian but are really just a reflection of the crisis we have brought upon ourselves. Others include a ban on the sale of fast foods at or near school gates, ridding hospitals of high carbohydrate snack machines, an increase in bariatric surgery, investment in weight management programmes and NHS staff broaching weight with obese patients. I say hallelujah. Vending machines should never have been allowed in hospitals in the first place and why teach children about healthy eating in school only to send them out to council licensed fast food at the gate?

The academy, which represents 200,000 doctors, has also called for advertisements for food high in fats, salt and sugar to be banned before the 9pm watershed. That should help parents by cutting down on pestering.

The UK is becoming the fat man of Europe and there's no excuse. My heart goes out to people who are struggling to feed a family on a low income. But as we learned recently, the fattest children are not the poorest – they are the moderately well off. There's a toxic combination of self-indulgence and laziness at the root of our growing malaise.

I'm part of it. I need to shift a couple of stones. I need to cut my portion sizes and take more exercise. And every day I swear I will do just that – tomorrow.

I know what to blame for my excess weight. I blame me. And I know who to blame for the 31% of Scottish children age from seven to 11 who are overweight. I blame their parents. They can't eat what their parents don't buy. It's really that simple.

The state would prosecute parents who gave their children cigarettes or alcohol. A high sugar/high fat diet can be every bit as lethal.

I know how tempting supermarket aisles can be. But a supermarket's priority is a high profit margin. Looking out for the family's health is up to us.

I no longer have to feed a family of hungry children but when I did I was never tempted to buy fizzy drinks and fast food. It doesn't fill them up. It makes them overactive and cranky. Pizza and Coca-Cola were rare treats not proper fuel for everyday living. But when we write about food or read about eating habits there's a delicacy about saying these things. We're frightened of offending someone. It is condescending bunk.

I remember when Gillian McKeith had her television series, You Are What You Eat. She repeatedly visited middle-class families who lived on ready meals and couldn't distinguish one vegetable from another. Some didn't know the difference between an apple and an orange.

I accept that people are time poor; that increasing numbers, worn down with the worry of stretching every penny, have difficulty finding the energy to get in from work and start cooking. It's so much easier to buy ready made. We've all done it. We've all (probably) eaten horse.

But. But. Don't we all know by now that we shouldn't do it regularly? Is there anyone left in Britain who hasn't heard about healthy eating, your five-a-day, about a balanced diet, about the need to exercise?

And still the numbers of obese people keep rising.

Encouragement and education isn't working. Perhaps it's time for the stick instead of the carrot. Perhaps it's time for financial penalties and starting with a tax on fizzy drinks seems appropriate since they have no nutritional value.

My only quibble is this: why stop at a 20% tax? That bottle of Coca-Cola I'm looking at would only go up by 38p. I don't think that's a big enough deterrent. The tax should be 40%, 50% or more. Better that rise in tax than an equivalent rise in the numbers of obese people dying prematurely.

We have to get serious about this epidemic and its cost to the health service. They say there are two certainties: death and taxes. Better to pay the tax if it delays the death.