Skipping breakfast and your fat cells |
Norman Swan: Let's start though with what happens to your fat cells when you don't eat until midday. A British research group has published the results of a trial comparing the effects on abdominal fat cells in lean and obese people who are either eating breakfast or holding off until midday. The lead author was Javier Gonzalez, who is Associate Professor of Human Physiology at the University of Bath, and his on the line from Bath. Welcome to the Health Report.
Javier Gonzalez: Thank you.
Norman Swan: What was known before you did this study?
Javier Gonzalez: So there's a lot of observational evidence of breakfast consumption. So we know that people who regularly consume breakfast are typically less heavy than other people, so they tend to have less body fat, but they are also healthier in many other ways, so they are more likely to be physically active and drink less alcohol and so on. So we didn't know whether this was a cause and effect of breakfast consumption…
Norman Swan: Or just the nature of the person who has breakfast.
Javier Gonzalez: Exactly, or any one of these other confounding factors actually influencing their body weight or their health. So this was one of the first randomised controlled trials to look at specifically energy balance and metabolic health of people when they either skip breakfast or eat breakfast.
Norman Swan: So I've kind of described the study, but why don't you just talk about it in a little bit more detail.
Javier Gonzalez: Sure. So we took two groups of people actually, so a group of lean people and then a group of obese people. And each of those were then randomised into two further groups where they either skipped breakfast every day for six weeks, so they were asked to not's consume anything with energy in, so they couldn't either consume food or drinks containing energy, so that was water only until midday every day for six weeks. And then the breakfast group were asked to eat at least 350 calories within two hours of waking, and at least 700 calories before 11am. So it was quite a substantial breakfast but, being one of the first studies in this area, we wanted to demonstrate a proof of principle.
Norman Swan: And was this poached eggs and bacon, or toast and muesli? What was it?
Javier Gonzalez: It was self-selected, so they were free to choose what they wished, but we did monitor what they did choose. And it was typically a very high carbohydrate breakfast, it was your toast and cereal and orange juice…
Norman Swan: More on the cornflakes end of the scale, okay.
Javier Gonzalez: Yes, exactly.
Norman Swan: And you are monitoring what happened to their fat, so tell us what happened.
Javier Gonzalez: Yes, so before and after that intervention they all came into the laboratory. All of them were in a fasted state, and we took some fat biopsies. It's a little bit like liposuction but on a small scale, so we only take about a gram of fat tissue.
Norman Swan: Dammit.
Javier Gonzalez: Yes, people always ask for more to be taken. And then we assess that for various things. So one of the things we looked at was gene expression, which is the activity of genes. So our genes can be switched on and off to different extents. And what we found was that specifically in the lean individuals the genes that were involved in fat metabolism, so burning fats, they were up-regulated or they increased their activity in response to skipping breakfast.
Norman Swan: So does that mean they were burning fats preferentially?
Javier Gonzalez: We can't really say they were burning fat because we were only measuring the gene expression, but it does suggest that those pathways in fat metabolism were increased. So yes, it was a suggestion that they were…their fat cells were switching to fat as a fuel.
Norman Swan: And what about the obese people?
Javier Gonzalez: Interestingly we didn't see that in obese people, and there were a number of other things that we saw in the lean group that we didn't see in the obese group. So it seems like the obese group were more resistant to the intervention of breakfast versus fasting. They seemed to respond similarly regardless of meal timing.
Norman Swan: And they were quite frugal in the way they burned sugar as well.
Javier Gonzalez: Absolutely, yes, that was another difference we saw between the lean and obese groups. So we also exposed these fat cells to insulin, which under normal conditions that hormone is potent at stimulating those fat cells to take up sugar out of the bloodstream. And in lean individuals we saw that really robust response, and actually by regularly consuming breakfast it increased people's fat cells from lean people, it increased their ability to take up glucose, but in the obese people they had a lower ability for their fat cells to take up glucose. So we can say their fat cells were resistant to the effects of insulin.
Norman Swan: So hold on a second, just to be clear then, so in lean people when they had breakfast, their metabolism was more efficient and effective. In other words, their insulin was more sensitive than fat people and obese people?
Javier Gonzalez: Yes.
Norman Swan: And, reading your paper, obese people, you interpreted the response as them trying to protect themselves from laying down more fat.
Javier Gonzalez: Yes, so this insulin resistance in the fat cells from obese people, it seemed to be perfectly proportional with the amount of total body fat they had. So it does suggest that because glucose is important in the process of storing fats, it seems like it's a down-regulation, their fat cells are turning off their ability to take up glucose and store fat.
Norman Swan: So tell me what the conclusion then is in terms of horse and cart, chicken and egg here with breakfast?
Javier Gonzalez: So what is clear is that by regularly consuming breakfast people tend to be more physically active, and that's not going to the gym, it's your spontaneous activity that you are not aware of…
Norman Swan: So you think it's cause and effect, breakfast does that to you?
Javier Gonzalez: Yes, we can say that from this study. Because it was a randomised controlled trial, people were randomised to consuming breakfast, so we removed all of those other confounding factors. So people were more physically active, but they did eat more too. So the net effects with weight loss isn't clear, but for health parameters there is a hint that certain aspects of health are improved by breakfast consumption.
Norman Swan: There are lots of people who are overweight who try and do their own version of the 5/2 diet, as I said in the introduction, by skipping breakfast and stressing themselves metabolically for 12 hours. What does your study say, if anything, of the sense of doing that if you are overweight rather than lean?
Javier Gonzalez: So given that there is no major effects on energy balance, I'd suggested that the method that people prefer would be the one to go for. So if you are someone who does like to consume breakfast, then you can be aware that the benefits of that are you are likely to be more physically active throughout that day. If you'd like to try some form of intermittent fasting, then just be aware that your physical activity levels might drop a little bit, and while you might get some of the benefits of increased fat metabolism, be aware that physical activity might drop. And of course you can counteract that, you're aware of that and you can perhaps time your physical activity or your gym sessions.
Norman Swan: Javier, thank you very much indeed. I'm not sure if I'll have breakfast tomorrow morning or not, I suppose it depends whether I go to the gym.
Javier Gonzalez: Yet, sounds good. Great, thanks for having me.
Norman Swan: Thanks for coming on. Javier Gonzalez is Associate Professor of Human Physiology at the University of Bath.
Copyright © 2017 Australian Broadcasting Corporation
.