I have a paunch. Not a big one, but a definite paunch. To add to it my blood pressure and cholesterol are a little higher than they should be for a man of my age. In fact that’s part of the motivation for my exercise regime.

Unfortunately, while I feel fitter and have lost a kilo or two, I still have a paunch, and this annoys me. I feel I ought to be able to get my weight and cholesterol down by exercise but it’s not happening.

And then I watched Michael Mosley’s program about weight reduction yesterday. Essentially he chronicles current research into calorie restriction and describes his own adoption of a 5:2 strategy (five days eating normally and two days or a restricted intake of around 700 calories (slightly under 3000kJ).

Normally I’m extremely cynical about these kind of diets, but I also used to be an evolutionary biologist and psychophysiologist. (A long time ago, and I’m not up to speed but it does mean I can understand and assess arguments and know the basic physiology discussed).

Now there are these people who live on nuts and fruits and eat less than 1900 calories a day, and it does appear that such a diet does deliver benefits in some cases in terms of longevity and elevated levels of bad things in the bloodstream. This is not terribly surprising, as it’s probably not that different from the sort of diet our primate ancestors ate, and is still eaten by chimps and baboons.

Baboons, of course are monkeys, but as they live in savannah and veldt, rather than jungle, they may be a better model of our early ancestors behaviour than our direct cousins, the chimpanzees and gorillas, who are forest dwellers.

Baboons spend a lot of time eating, or more accurately foraging. Getting enough to eat is hard work for a baboon which is why they do hunt and kill small mammals, and in the process take the first steps towards co-operative hunting and enhanced communication.

We could say that baboons, because of their primarily plant based diet, are in near permanent calorie restriction.

One of the claims for calorie restriction is that the body repairing itself more and another is that it improves neural/sensory performance. Both make evolutionary sense, it being better in energetic terms to fix than make anew, and that in times of hunger your sense need to be more alert to the opportunity. Wether it’s true or not is a different question.

We also know that a plant based diet is good for cholesterol reduction so a move to that sort of diet makes sense, but, as I know from the years I was a reasonably strict vegetarian, you have to eat a lot of veggies and it can make life difficult if you are out in the world.

Interestingly we know now that just eating a bit less and exercising more can bring substantial benefits. After the Soviet Union collapsed Cuba lost it’s access to cheap oil, and a means of raising currency for food imports. The government rationed basic foods, encouraged people to grow their own vegetables, and if people needed to get anywhere they had to walk or ride a bike as there was little or no fuel for buses or trains. There was little or no private transport in Cuba, so the loss of public transport meant cycling on cheap imported Chinese bikes, or walking.

Cuba also has an excellent health system so they could record the effects of the period of austerity. We can treat this as a large scale experiment in calorie restriction and the adoption of a more plant based diet. It’s also a plug for increased physical activity.

So let’s ratchet froward from baboons to humans and to hunter gatherers and in particular the San of South Africa and Botswana. There were a few anthropological studies done on the San before they became heavily exposed to the joys of western society.

One outcome of the studies was that the San, or more accurately San women and children, spent a lot of time foraging for plant based foods, while the men seemed to basically do a bit of hunting, plus the San equivalent of sitting around and bullshitting. The understanding of the physiology of calorie restriction was not well understood at the time, but it was generally agreed that meat must provide a range of important additions to the diet not easily obtainable from a diet of nuts and roots.

As meat tends to come in antelope sized lumps, the San will tend to have a number of days where they have enough to eat followed by some days when things don’t work out, something that is mimicked by the 5:2 diet – 5 days when you speared the antelope and two days when things just didn’t work. There’s nothing special about the 5:2 ratio, it just fits into a seven day week. A 10:3 ratio would probably work just as well.

So what we have is a set of three components for weight reduction

• increased plant based diet – we eat a lot of plant fods already but this probably means more wholegrains and less bread and pasta
• increased exercise – happening already
• periodic calorie restriction – meaning we eat less

The interesting thing about periodic calorie reduction is that people seem not to eat to excess on full days to compensate – and as someone who is careful about what I eat I don’t see a problem.

So, always the scientist I’m going to experiment on myself. I’m not going to be as strict as the regime Michael Mosely has developed but two days a week I’m going to skip dinner and have a smaller bag lunch, while eating the same size breakfast, which should roughly halve my calorie intake on those days. I’m also going to record my weight and girth and see what happens.

This is not a real scientific experiment but more of a ‘what-if’. We’ll see what happens