Is What We Eat Making Us Fat?

Lots of us are fat, and we are getting fatter. It is most pronounced in the US, but the UK is not far behind. The Anglo Saxons have it worse, but Europeans are also showing alarming increases in obesity. Basically waistlines are expanding everywhere.

What is going on?

Well like all problems, there isn’t a complete consensus on the cause. One obvious explanation might simply be the availability of food. There is loads of it around. Despite the recession most of us still have enough cash to buy more food than we actually need. So is it simply that we don’t have the will power to cope with all the tempting treats that are on offer? That sounds quite plausible at first sight. It also puts the responsibility squarely on us as individuals, which is something that a lot of us like to hear. We just have to learn to curb our desires and we’ll be fine. There is still a majority that isn’t overweight, so we must be the virtuous ones. Obesity is therefore a moral rather than a medical issue. Lay off the pies and you’ll be fine.

But does it fit the facts? Why are the Americans fatter than the British for a start? About 30% of Americans are obese, and only 20% of British. And why are the British fatter than the French? Only about 10% of French are obese. If it was simply a question of having enough money to buy all the food we could eat, surely all three areas would be equally obese. Be honest, cultural differences there may be but do we really think that the French have twice the willpower of the British and three times that of the Americans.

In fact look closer at the details and the link between obesity and how rich or developed the country is is not very clear at all. The US tops the table, but Mexico is not far behind it. Now Mexico is one of those countries whose economic performance has been pretty impressive lately, but even so it has not yet caught up with Britain. And yet Mexicans are more obese than the British, and not far behind the Americans. In Europe itself it isn’t the richest who are fattest. The British are the fattest, but are not the richest. The French, who are about on a par with Britain income wise, have about half the level of obesity.

Not that I would be complacent if I were French. At 11% of the population, French obesity problems are pretty severe. They are just in a better state than we are.

So what actually is going on?

It looks very much like it might be a lot to do with the type of food we eat. One of the characteristic features of the American diet is the use of high calorie ingredients, in particular high fructose corn starch (HFCS). One suggestion that has been made is that this agent is somehow responsible for American obesity.

This isn’t nearly so widely used in Europe, so it isn’t immediately obvious that this is the case. If the HFCS is the problem, shouldn’t the Europeans be normal in weight? But although Europeans don’t have that particular ingredient, we still have plenty of processed foods that have become more widely eaten over the last 5 or 6 decades. If we have a look at the chemistry behind them I think it might make things a bit clearer.

A Quick Guide to Sugar Chemistry


Everyone has heard of carbohydrates, and they are one of the few classes of chemicals that are familiar enough to have had their name shortened in everyday language. Most people have a good idea what ‘carbs’ are.
It is a bit of a shame that this name, which dates back to the earliest studies in nutrition, tells you so little about them. It simply indicates that they are made up of carbon and hydrogen, which doesn’t get us very far. A less well known name is polysaccharides, which is a lot more informative, because carbs are basically strings of sugars. A carbohydrate is hundreds of thousands of glucose molecules strung together like a bead of pearls. If you want to get an idea of just how close the relationship between carbs and sugar is, put a bit of bread in your mouth and rather than swallowing it chew it for a few minutes. You’ll soon notice the sweetness developing.


What is happening is that an enzyme called amylase in your saliva is splitting up the carbohydrate chains into individual glucose units. These are small enough to easily get out of your digestive system and quickly show up in your blood stream. Glucose is the body’s energy source, and you need to keep your blood glucose levels high enough to keep going. The amylase is just one part of a co-ordinated system of glucose management.


Historically humans used to get the bulk of their energy from carbohydrates, but in the modern world we also get a big proportion of them from sucrose, or just plain sugar. This is sweet as soon as you eat it because it has already been broken down for us during processing. Rather than having hundreds or thousands of sugar units, it has just two. One is glucose, the other is a slightly smaller sugar called fructose. I always think that this structure makes it look a bit like a man and a woman holding hands, with the man being just a little larger.  The body however is not so fanciful simply splits the molecule up into a unit of glucose and a unit of fructose.


Although glucose is the main energy bearing sugar in the body, fructose is a common enough sugar and we are equipped to handle it.

I have done a blog post on the chemistry of the sugar we eat if you want a bit more detail.


So on the face of it there doesn’t seem to be much or a problem here. The energy we need can be derived from carbs, sugar or high fructose syrup and the end result is always the same. We end up with glucose or the fairly similar fructose in the blood stream, both of which are perfectly safe and indeed perfectly natural.

Life however, sadly isn’t that simple. There’s a well known phrase, the dose makes the poison. Chemicals can’t be characterised as safe or dangerous. The most dangerous chemical on earth, which I guess is plutonium, is harmless at a low enough level. And the most innocuous, which could easily be glucose, can still be harmful if you use enough of it.
Sugar in your blood and brain

You may or may not be interested in the chemistry of your food, but even if you aren’t your brain certainly is. There is some mechanism by which your brain monitors your blood sugar levels and processes that information. People have been put into brain scans and shown pictures of different foods. The ones that lead to the highest increase in blood glucose levels provoke the strongest response, even though the person being scanned has no conscious awareness.

Have you ever wondered why everything you like is bad for you? This would be the reason. You have circuits in your brain that train you that way. And now you also know why it is so hard to keep to a diet. Your subconscious brain is subverting your intentions all the time.

If you want some fun with this information, next time you are at a buffet see if you can spot which items have the biggest sugar hit, and observe that they are the ones that will vanish first. Here is a hint to get you started – lettuce leaves don’t do much for your glucose levels.

When you analyse it, what is happening is that the brain is pushing you to feed its need for energy by getting the quickest and easiest source of blood sugar it can see into your mouth. Your conscious brain is well aware that the supermarket is now open seven days a week and the last thing you need to do is stuff yourself with as much as you can eat. But your subconscious brain hasn’t got that message yet. It is still working on the basis that if you don’t eat now you might starve tomorrow.

What you can do

But the more interesting question is how does this help us lose weight, or avoid putting it on?

The implication is that the key is maintaining an even blood sugar level. If you let it drop too low your subconscious will send you out on a search for the most fattening thing it can lay its hands on. If you overdo it, your body will start squirrelling away the sugar into fat deposits. And it will then attempt to preserve those deposits by making you hungry again.

So the trick is to make sure you are never hungry, and avoid foods that elevate your blood sugar.

There are a number of things that might help. The most obvious is to avoid as far as possible sources of highly processed and easy to absorb sources of sugar. HFCS must be about the worst thing to include in your diet from this point of view. But sucrose is not far behind. A much better source of energy would be polysaccharides that take longer to be broken down and absorbed. But you also need to keep the rate you eat them down as well. You are in effect eating a lot of sugar quickly if you eat a sandwich. The obvious alternative is fruit and raw vegetables. These take a lot longer to chew and to break down so don’t spike your blood sugar.

Fat in your diet has the effect of slowing down absorption as well. So if you have to have a slice of toast at least put some butter on it. (A great experiment is to try eating toast without butter in the morning, and see how quickly you feel hungry during the day. Try it, you’ll be amazed.) Drink full fat milk. It has more vitamins anyway, and tastes better too. A less obvious one is drinking a small amount of alcohol, say a glass of wine, before or with a meal. It reduces the speed at which glucose is absorbed as well. I’d love it if that turned out to be the explanation for the difference in obesity between the French and the English.

Above all, take your time to enjoy your food.

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Further Reading

I wrote this post about a year ago and then forgot all about it until I saw the publicity for the BBC programme The Men Who Made Us Fat.   I posted it in a bit of a hurry just before the show aired, as I didn’t know if I was going to agree with what it said or not and I wanted to get my own thoughts out first.

In the event there was quite a bit of overlap (here is my review of  The Men Who Made Us Fat )which was interesting in itself.

Having seen the programme and reread my post, I felt that some people might want a bit more detail on the chemistry, so here is my quick and easy guide to the main sugars in food.

Here is where I got my obesity statistics from.

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