Thursday, May 28, 2009

Review of 10 Things You Need to Know About Losing Weight

I managed to watch 10 Things You Need to Know About Losing Weight (BBC 1, 9pm) last night without throwing anything at the screen - click here for a link to the program (may be available in the UK only) or here for a related BBC Magazine article - but this may just have been because my hands were occupied taking notes so that I could blog about it.

Here are the 10 things:

  1. Not sure what they called this, seemed to be a variation on: Don't go shopping when you're hungry. The presenter had his brain MRI scanned, firstly on a full stomach, on a second occasion on an empty stomach, and while being shown pictures of food. His brain 'lit up' more in response to 'high calorie' food (chocolate eclairs) than 'low calorie' food (cucumber slices) when he was hungry; whereas when he wasn't hungry the response was the same.

  2. Use of an expensive machine to discover the bleeding obvious: when you are hungry, you are more interested in food and, more than that, more interested in food that your brain knows (from prior experience) is more likely to provide you with calories. Actually, I suppose this kind of research is necessary - we should investigate 'what everybody knows' - and try and disprove it - that is the scientific method. It also raises another interesting point - which wasn't mentioned in the program (although to be fair it isn't strictly relevant). Why doesn't the hungry brain respond to pictures of fruit and vegetables? Perhaps it's because humans didn't evolve chewing their way through bucketloads of plant matter for hours?

  3. Use plate size to trick the brain about portion size, i.e. use a smaller plate - less food will look like more.

  4. Personally, I think this works, I've used it with children the other way round - i.e. put the food on a larger plate and it looks like less so they eat it up. However, if you don't eat 'enough', you may end up hungry later on and snack!

  5. Count calories - save a few here and a few there e.g. have black coffee instead of cappuccino, and it will add up to fewer calories over the day/month/year, leading to you magically losing weight.

  6. Or maybe you'll just be hungrier? Has there ever been a controlled trial of this idea to see if it actually works?

  7. Fat people eat more than they think they do.

  8. Actually this was the most interesting point and worth a separate post of its own.

  9. Eat protein because it leads to greater satiety.

  10. This was demonstrated with a small-scale experiment during the programme. It has been shown by studies.

  11. Liquid food (as opposed to drinks with food) fill you up for longer. This was also demonstrated with an actual experiment.

  12. This point is different from the preceding one: the mechanism here is one of the physical constraints on digestion, whereas the fullness from protein comes from the release of a hormone (PPY) which interacts with other appetite regulating hormones (leptin, ghrelin). If you use soup to 'trick' your body into eating fewer calories than usual, you will likely eat more at the next meal, once the soup has been digested.

  13. Choice causes overeating.

  14. I thought the 'experiment' conducted to show this was quite poor. Two bowls of equal quantities of sweets were left out in an office canteen with a sign Free Sweets: one bowl was obviously smarties, the other bowl held purple smarties only. The smarties all disappeared, the purple ones didn't. A better comparison would have been smarties vs. chocolate buttons (they're all the same). The purple smarties looked vaguely medicinal - how do we know that didn't put people off?

  15. Calcium in dairy binds fat which you then excrete: over a month this can save you calories.

  16. In fact, it saved the guinea pig in this experiment slightly more than 5g of fat per day or about 160g per month. (Sounds like a lot? - I eat that much fat every day! I'm not going to quibble about the loss of one day's consumption per month.) Interesting - bad for dairy's image as a source of calcium - how much of the dairy calcium is lost this way? Also, the presenter felt constrained to recommend 'low-fat' dairy for this strategy. Noteworthy that this was the only vestige of 'low-fat' dogma in the programme. On the other hand, if it truly is 'low-fat' dairy then there isn't much point is there - where's it gonna find the fat to bind?

  17. Exercise - another interesting one. An experiment with the presenter on a treadmill showed that 90 minutes of fairly fast-paced walking (he was quite breathless after it) only burned about 19g of fat (171 calories).

  18. Given that after 90 minutes of fast-paced walking you've probably built up a bit of an appetite, it isn't going to do much for weight loss is it?
    However there is a punchline - an 'afterburn' effect where exercise boosts 'fat-burning' into the next day. So this could work - but there is still that question: why will the greater amount of calorie burning going on, not prompt your body to ask you for more food?
    Update: the effect of exercise to promote 'fat burning' is disputed by research - see article here.

  19. Small amounts of extra movement during the day e.g. take the stairs instead of the lift, will boost your calorie burning.

  20. Can't argue with this really, but the effect will be small (90 minutes on a treadmill = 171 calories) and once again it ignores the hormonal elephant in the room - which will be tackled in the next post about point 4.

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