It's a health issue.
Obesity-related illnesses are awful and debilitating and expensive for the nation and I totally agree it would be much much better if we were all fit and healthy and the best we could be.
No argument here. I've been fat and I've been obese and I've been a healthy weight. I go in and out like an accordion. Right now, I'm considered normal on the BMI scale, which takes some doing when you consider most of the All Black front row are obese according to that particular measure of health.
And I'd like to think at 50 I'll stay normal for the rest of my life, but who knows? The thing that annoyed me about Gareth's call for a fat tax, and indeed for the researchers' call for a tax to be imposed on fatty foods, is that he knows, and they know, that it doesn't work.
The Danes, who are very sensible people and whose government appears to always have the interests of their citizens at heart, introduced a fat tax in 2011. By 2012, they'd scrapped it as unworkable. Proponents say sniffily that the tax was scrapped for political reasons, not health reasons, but at least one of the researchers appears to be driven by politics as well.
Professor Cliona Ni Murchu, of Auckland University, says a fat tax on beef and poultry would limit people's consumption of those foods and that would have an effect on greenhouse gas emissions as well. Eat lentils, save the planet.
I accept that a lot of rubbish food is cheap. When you're struggling to make ends meet, a $5 burger and chips meal seems like a good deal. But that's only if you've never learned how to make your own.
Offering people choices is the answer, not bludgeoning them with the blunt stick of taxes.
When I was at school, I did Latin and French. I was also a boarder, so I knew nothing about cooking. When I went flatting, I bartered my way out of cooking nights and it wasn't until I became a mum that I learned how to cook.
I had a year's grace until the child was on solids and then I had to step up. So I turned to my mum and other wise women I was lucky enough to know and learned how to stretch mince with leftover rice and rolled oats and finely chopped vegetables from the fridge that were one day away from the compost.
I learned how to make delicious soup from a pack of imperfect vegetables sold at cut price and I picked up bargains from the supermarket by browsing the aisles at night, choosing chicken and meat two days off their use-by dates and turning them into casseroles.
But people on the bones of their arse who don't have that sort of support or knowledge to tap into don't really have an option. You can't know what you've never learned. I wish we could set up food caravans close to fast food outlets and have cooks showing people how to make real burgers - nutritious, cheap - so they don't have to spend their money on crap. Then, once you know how good it feels to eat food that is pure and good and honest, you won't have the same taste for over-sugared, over-salted, over-processed rubbish, sold for profit.
Don't get me wrong. Rubbish is fabulous once in a while. I had fish and chips and a couple of beers before the Super 15 final last week, and loved every saturated fatty, salty morsel of it. But I wouldn't like it all the time, and I guarantee if people knew how to turn real food into cheap, healthy meals for their families, they wouldn't either.
Kerry McIvor is on NewstalkZB, Monday-Thursday, 8pm-midnight.