Every time the news is switched on, it seems there are new statistics being pulled out on the rise of obesity in Britain. Obesity which, so they say, will put added pressure on our NHS system as heart disease, diabetes, cancer and other health problems become more prevalent. But what's really causing it?
The prevalence of processed food, our sedentary lifestyles and the convenience of having fast food outlets on every high street are all factors, I'm sure, for our bulging waistlines. But a portion of chicken nuggets or a burger once a month probably won't affect your weight too much. The problem, from where I stand, is with everyday portion sizes.
When did you last order a meal from a Chinese takeaway and finish every scrap of food - even the free bag of prawn crackers? Or stuff those last few chips into your mouth knowing that you already feel full, but just can't stop yourself because they're there.
We're brought up as kids with this feeling that we need to finish everything on our plate, and I think that continues into adulthood. If we've paid for a plate of food, we feel cheated if we don't finish it - because in our mind, we're wasting money as well as the food. In short, whatever the portion size is, we'll eat the food because it is there. A 2005 study by Brian Wansink found exactly this. Participants were given a bowl of soup to eat. For half of the participants, the bowl was secretly filled up from underneath the table. When questioned afterwards, the group that had eaten almost twice the amount of soup than the others said they felt no more hungry or full than the other group.
Marking things low-calorie or 'healthy' doesn't do any good either. Another study by Provencher et al in 2009 found that when something was labelled 'low calorie', people ate 35% more of it than when it wasn't labelled in this way. It's as if we're giving ourselves permission to eat more, just because it has a label stuck onto it. It's important to know that 'healthy' doesn't mean you can eat loads of it, though. Seeds and nuts are considered 'healthy', but some also contain fat, so should be eaten in smaller portions.
The Food Standards Agency conducted a review of portion sizes in the UK in 2008 and found that ready meals, some fast food items and sharing packs of crisps were among those that had increased in portion size since the 1990s. Some chocolate packets had reduced in size, but these were mostly multipack bars and not designed to be sold on their own. And in 2007, a study by Young and Nestle concluded that portion sizes generally in Europe were larger in 2006 than they were in 1998.
But portion sizes aren't just getting bigger in shops and restaurants, which are caught between trying to do the right thing for nutrition and still give people value for money. We're dishing up monster meals at home, too. Next time you cook yourself a bowl of pasta, weigh it first. A recommended serving of pasta is about 75g-100g per person. And a portion of cooked rice is about the size of your fist. I was talking to a lady the other day who said she was cooking roast chicken for her family of four and was complaining how she had to buy two chickens because her 'growing boys' (both teenagers) eat half a chicken each. (The recommended portion size for meat and poultry being about the size of a pack of cards).
So don't fall into the trap of mindless eating: if you snack throughout the day on some wholegrains, fruits and a handful of nuts and seeds, you'll feel like eating much less for your evening meal anyway. And slow down - it takes 20 minutes for your brain to know that your stomach is full - so don't bombard it by throwing food in there before it's had a chance. I've spoken to a number of doctors recently who have all told me that a 'little and often' approach to eating is much more friendly to your digestive system than three Olympic-sized meals a day. In fact, all this reminds me of a Twitter convo between Man vs Food presenter Adam Richman and a fan. The fan asked him how he managed such dramatic weight loss over the last few months. Adam's reply? 'Less.'
What do you think? Are portion sizes too big? Do you feel comfortably full after eating (in restaurants or at home) or do you most regularly feel stuffed and need to lie down?
For more information on portion sizes have a look at a leaflet published by the World Cancer Research Fund.