Foods that make some of us put on weight can have little effect on others, according to research being carried out in Israel. It might be time to rethink the way we diet, writes Dr Saleyha Ashan.
Like most of the population, I must admit that I am on an eternal quest to lose weight. For me it’s more to do with concerns about health than aesthetics. I have polycystic ovary syndrome and a family history of type 2 diabetes and that puts me into a high risk category for developing diabetes myself.
I have always watched what I eat - and yet I never seem to shift the weight, while friends seem to eat what they want without putting on a single bulge. It seemed like they could just "break all the rules". But perhaps that’s just because we have been wrong about what "the rules" of diets are.
Last month, I travelled to Israel for Trust Me, I’m a Doctor to take part in a vast new research study being carried out there by a team at the Weizmann Institute of Science. They are in the process of monitoring 1,000 people in absolutely minute detail to see exactly how their bodies react to food - and their first results are rewriting the textbooks on our relationship with food.
When we eat, our blood sugar level rises - and both the speed at which it peaks, and then how quickly our bodies deal with that and get it back to normal, is very important to our health.
Foods have, therefore, been traditionally classified by how much of a blood sugar spike they cause - with "high GI" (Glycaemic Index) foods being thought of as bad for us, and "low GI" as good. Every nutritionist would tell you this. But the Israeli research, led by Dr Eran Segal and Dr Eran Elinav, suggests that it is simply not so.
因此，依据会引起血糖升高的多少，食物在传统上被划分为对身体有害的“高GI（血糖指数）”食物和有益的“低GI”食物。每一个营养师都会这样告诉你。但是由 Eran Segal 和 Eran Elinav博士带领的以色列研究团队表示，并不是这么简单。
Once I arrived in Tel Aviv, the team not only took all my vital statistics and medical history, but they gave me a little implanted glucose monitor under my skin, which would monitor my blood sugar levels constantly for the next week. The team’s nutritional experts had prepared me six days of menus specifically designed to test my body’s response to a few standardised meals, mixed in with some of my personal staple foods.
I’m an accident & emergency doctor, which is something that undoubtedly has an effect on my diet.
I never buy bread - it’s an aisle I just don’t even go down in the supermarkets and I live in fear of sandwiches - but I see other people living on them.
I do, however, reach for the grapes - I love them. I can eat bunches of them and feel guilt-free doing so. They are my go to "healthy" snack. Another guilt-free grab is sushi. I snatch a box of salmon nigiri and am off. Now, though, had come my chance to find out what each of these foods was really doing to my body.
Other things, such as stress levels, exercise and sleep can all affect our blood glucose responses, so the research team made me log everything I did throughout the day on a little phone app.
For the next week, Leila and I did and ate exactly the same things together - eating in the same restaurants and carefully weighing our food to ensure that it was as identical as possible. Textbooks said that our bodies should respond to them in a similar way. The Israeli researchers suspected that we wouldn’t.
A fortnight later when our results came through I could not have been more flabbergasted. Virtually all my "healthy snacks" such as grapes and sushi caused me big blood sugar spikes, as did a chicken sandwich, and cereal. On the "good" menu, though, was chocolate, ice cream and regular cola.
No-one seems to have suspected this degree of individual variation existed, simply because such a controlled study on so many people has never been done before. There is, it seems, no such thing as a "high GI" or "low GI" food - it depends entirely on your own body. But why do our bodies vary so much? Well, the team also have a handle on that now too - and it’s an answer that has exciting implications.
Along with our roster of health tests, Leila and I both also gave the researchers a stool sample. From this, their laboratory was able to discover the composition of our gut microbes. We all carry thousands of different bacteria, viruses and fungi in our guts, which not only help break down the food that we eat, but also produce a huge range of compounds that our bodies absorb and which can influence almost every aspect of our lives, from our immune system, to our metabolism, to our neurotransmitters.
By comparing the gut microbes of the hundreds of study volunteers with their blood sugar responses, Segal and Elinav have been able discover that our microbes might be the key to why our blood sugar spikes with different foods are so individual. The chemicals they produce, it seems, control our bodies to this extent. What is particularly exciting about that fact is that - unlike our gene - we can actually change our microbes. And that is very good news indeed for any of us who find that our favourite foods turn out to be "bad" for our blood sugar levels.
通过将几百名志愿者的肠道微生物和他们的血糖反应作比较，Segal and Elinav 已经能够发现，微生物可能起着至关重要的作用，它导致不同的食物引起血糖峰值的个体差异。看起来应该是微生物产生的化学物质，将我们的血糖控制在某种程度上。这一事实尤其令人兴奋的是，我们改变不了基因，但微生物却是我们可以改变的。这是一个非常好的消息，对每一个人来说都有了解决办法——当发现我们最喜欢吃的食物会影响自己血糖时。
When it comes to my own microbes, at the moment I have a mix of good news and bad. The variety of different types of gut bacteria I have is limited and that’s not ideal.
Healthier people, it seems, have a wide diversity. It was a huge surprise to me that there could be such a link between microbes living in my lower gut and a condition like that.
Elinav and Segal assured me, though, that by adhering to the diet of foods that my gut bacteria like, I should actually be able to change the composition of them. This in turn would have wider impacts on the rest of my health and wellbeing.
不过，Elinav and Segal博士向我保证，只要根据肠道细菌的喜好来调整饮食方式，微生物的组成其实是可以改变的，这反过来也能对我的幸福健康产生广泛的影响。
So, armed with my list of "good" foods, I am now embarking on a second phase of the study. I am going to see if I can change my own gut microbes. My results showed that although I do have a good balance between two major groups of bacteria, I am missing a third group almost completely, which could be a key to a healthier weight, and I am also lacking in microbe diversity.
Over the next month, I shall be sending regular little parcels to Israel for analysis, and hoping to see that change as I adapt my diet.
The team at the Weismann Institute are continuing their work with a huge year-long study now into how people can improve their gut microbes. Their dream is that anyone, from anywhere in the world, will soon be able to send in a small stool sample, have their microbes analysed, and - without the need for a week’s blood sugar monitoring - be sent a personalised diet plan that will stabilise their blood sugar levels and improve their gut microbes.
As they say, the widespread obesity and diabetes epidemics show that whatever we’re trying now to improve our relationship with food simply isn’t working. It could well be that they have hit upon the key to this - that until now we have completely misunderstood our own bodies and how food affects us.
So, as I chomp on a chocolate bar and ice cream (although the researchers hasten to add that a nutritionally balanced diet is still as important as ever), I am looking forward to seeing whether I can start to lose weight and become healthier as a result.