A pair of groups of whom I have never heard before called the the National Obesity Forum and the Public Health Collaboration have made a bit of a stir in today’s newspapers by attacking government health advice. The official line is that obesity is caused by eating too much fat, so we should avoid it and go for low fat options. These activists claim that it is the other way around. We should eat plenty of fat and avoid processed carbohydrates. Who is right?
Well if you look at the history of health advice relating to what you eat the overwhelming probability is that both of them are wrong. We’ve been given all sorts of contradictory and often non-sensical suggestions about what we should eat over the centuries. My nan used to regularly take laxatives because she believed they were healthy. I have no idea where she got that notion from, but I have heard of other people of her generation doing the same. She certainly sincerely believed it. She also lived to a ripe age.
Part of the problem is that the scientific method just isn’t very good at evaluating claims made for the health benefits of different foods. You can do a study where you try and keep everything else the same and just vary the thing you are interested in. But the practical difficulties are immense. The reality is that it is very hard to generate empirical evidence for what is and isn’t healthy. And very few people are neutral about food choices. As a scientist I am prepared to accept that it might be possible that a vegan diet is more healthy than a conventional one. As a lover of bacon sandwiches, I have a vested interest in not believing it.
So what can we do?
My approach is to simply try things out on myself and see how they work. I know that this isn’t remotely scientific, but science hasn’t really helped solve the various debates about nutritional controversies.
I am continually trying to keep my observations updated, but what I have found from experimenting on myself is –
- Sugar in particular, but refined carbohydrates in general tend to make me tired, and to stimulate my hunger. I have never observed the ‘sugar rush’ of high energy that some people describe.
- Eating a lot makes me tired and also stimulates hunger – though with a time lag rather than straight away in the way that sugary foods do.
- Fruit and raw vegetables are very effective at staving off hunger, though they make me feel sick if I eat a lot of them in a single sitting.
- Exercise has almost no impact on my weight.
- Losing weight increases my energy levels, and my ability to endure prolonged exercise.
- Eating nothing by raw food for a number of days increases my ability to think clearly, and gives me the ability to get off to sleep in minutes and sleep deeply all night. However, but about day 4 I would literally murder somebody for a fried sausage or microwaved curry.
- Reducing my salt consumption has almost no noticeable effect at all.
- If I allow myself to become very hungry, I most crave fast foods or convenience food and they taste absolutely delicious. (I am normally not attracted to them.)
How many of these things apply only to my own particular metabolism, I have no way of knowing. I have a feeling that point 1 at least is reasonably common.
I have some theories to explain these observations, but on the whole I think it is better to try and plan your diet according to what you find does and doesn’t work rather than some idea you may have had or that you have picked up from somewhere. The state of our understanding of nutrition is obviously not yet at the point that we can use it as a guide to action. If it were, nobody would be interested in stories like this one. In the absence of firm knowledge, we have nothing to rely on other than what we feel.