3 intermittent fasting mistakes that cancel fat loss and stop you seeing the benefits | Prof James Betts

Jonathan Wolf (0:00)

Welcome to ZOE Science and Nutrition, where world leading scientists explain how their research can improve your health.

Annoying sensation of hunger overwhelms your mind, pushing aside all other thoughts. A deafening rumble emanates from your stomach, as your fridge calls your name. How can fasting possibly be good for you when it feels so wrong? In the not-so-distant past, going hungry was a necessity rather than a choice. But today, fasting is entirely optional, yet everywhere. From intermittent fasting apps to wellness influencers promising fat loss, longevity, and cellular cleanup. But what actually happens when we fast? And can it really improve our health? Although fasting is wildly popular, it's still hugely misunderstood and questions about does breakfast kickstart your metabolism? Does coffee, olive oil, or a splash of milk break a fast? And are the supposed benefits something unique to fasting? Or simply the result of eating fewer calories? Today, I'm joined by James Betts, Professor at the University of Bath, where he carries out fasting studies on humans. He's published dozens of papers on fasting, and is one of the world's leading experts on meal timing and its metabolic effects. By the end of the episode, you'll know what you have to do to be in the fastest state, what you can eat while fasting, and whether fasting is something you should try, or just another nutrition myth waiting to be debunked. James, thank you so much for joining me today.

James Betts (1:42)

Well, thank you very much for having me on the show.

Jonathan Wolf (1:45)

It's a pleasure. We always start the show with a quick-fire round of questions, designed to be very hard for scientists, because we have these rules where you can say yes or no, or if you have to, you can give us a one-sentence answer.

James Betts (2:01)

Okay, that's scary, but let's go.

Jonathan Wolf (2:03)

All right. Is breakfast the most important meal of the day? No. Is the time when you eat a meal important for good health? Yes. Can some forms of fasting improve your long-term health?

James Betts (2:20)

Yes. In brackets, it depends.

Jonathan Wolf (2:24)

Can intermittent fasting help some people lose weight?

James Betts (2:28)

No. Within brackets, it depends.

Jonathan Wolf (2:31)

What's the most common myth that you hear about fasting?

James Betts (2:36)

Probably something about the body going into starvation mode. People seem to think that their body will just stop burning calories if they fast.

Jonathan Wolf (2:45)

Well, look, I'm both fascinated by the answers and slightly confused. And so I suspect a lot of our listeners are in the same boat and probably coming in also a bit confused about fasting because there's so much talked about it. There's so many different people who have been telling us different stories over the last few years. Like, what is it? How do you do it? Which form is best? And of course, does it actually work and give you health benefits? I know you're really interested in something called nutrient timing. Can you explain what that is and why you think it's so interesting?

James Betts (3:20)

I believe then that when we really start getting into the weeds about fasting and meal patterns, ultimately as a physiologist, we back up to think about nutrient timing because we're ultimately focused on time here. As I often say to our students, it's the most studied variable in all of science. Whether you're into nutrition or biology or physics, time comes into all of our experiments because most parameters are not stable and we need to do pre-tests and post-tests. We don't eat continuously like rodents, which teach us a lot about our physiology.

Yet, our metabolism and our requirements just march on variable but continuously. Somehow, our body beautifully manages to match up these chunk meals with the things that we need in between meals as well. I would say nutrient timing is about how that flux or balance is met, how the body sees nutrients arrive at one time and either stores them or uses them or excretes them so that you have them available when needed.

Jonathan Wolf (4:21)

You're saying, as humans, we tend to eat discreet meals and in quite a short period of time, we get a lot of nutrients in, but then long periods where we're not eating anything and then another meal. That might sound normal, but actually you're saying even when you think about mice or whatever, they're actually just eating all the time. That's very different because our body is needing to use up nutrients, energy, whatever continuously. We've got this mismatch that our body somehow has to be designed to solve.

James Betts (4:52)