Unless you’ve been living under a log, you’ve heard of 5:2 fasting. You probably have a friend doing “5:2” and she’s probably really, really, grumpy on the days she doesn’t eat. I know I was when I tried it.
Michael Mosley made 5:2 fasting famous, and himself very rich, by exploring the benefits of fasting in his BBC documentary “Eat, Fast, Live Longer.” and applying the principles to himself by fasting 2 days per week and losing a boggins load of weight very publicly. The diet is so popular in the UK that some restaurants have 5:2 options on their menus.
Back in the 70s, if you wanted to get slim, you simply didn’t eat between meals. It would seem that people knew what they were doing back then. The average American woman now weighs the same as the average man in the 60s. My grandma used to tell me that bread and bananas made her fat, not butter, lard and steak. I think she may have known what she was on about too, but at the time we thought that was ridiculous; everyone knew fat was bad for you, so it must make you fat.
Somewhere along the way, the received wisdom became that to lose weight you have to eat all the time, six times a day. If you don’t then, oh no!, your metabolism will crash and then you will never be able to lose weight again. The idea was that your blood sugar and insulin levels stayed constant and, supposedly, you wouldn’t get hungry, but fat burning occurs when insulin levels are low and not only does fasting not wreck your metabolism, it actually seems to increase metabolic rate (1). On top of that there are psychological issues at play. When people snack, they reach for the treats. Even if you eat 6 healthy meals a day, it’s very hard not to underestimate how many calories there are in each tiny meal, and since you’re never full, you really want that tiny meal to be a bit bigger.
Well the pundits have done an about face and the benefits of fasting are now well studied and documented.
- Insulin levels drop, which facilitates fat burning.
- IGF-1 also drops, which, at least in rats, increases life span and reduces the risk of cancer (2).
- Human Growth Hormone increases (3), which increases fat loss and muscle gain.
- During fasting, the body undergoes cell autophagy, which is very good for your brain (4).
So fasting is good, but what about our grumpy friend?
Well, anecdotally, women experience fasting differently than men. While for men it might be an enjoyable ascetic practice, for women, like me, it can be a nightmare day of clutching your angry and painful stomach while waiting for the next opportunity to eat, followed by a day of gluttony. The reason, it is postulated, is that women are more sensitive to hunger signals for reproductive reasons. Fasting affects menstrual cycles (5) and therefore the ability to reproduce, so your body reacts strongly to any hint that a famine is on its way. From our gene’s point of view, reproduction is the only point of existence and so we are strongly programmed to protect our ability to do so.
Now meet Hugh Jackman, our very own Aussie pin-up boy.
Hugh practices 8/16 fasting. That’s 8 hours of eating and 16 hours of fasting. This type of fasting is not as well studied as fasting for entire days, but it’s assumed that it has the same benefits. Insulin levels drop over night and fat burning can take place. The other benefits of cell autophagy and reduce IGF-1 and increased HGH are assumed to also hold true.
Since women have such a strong reaction to fasting, 10/14 is recommended for us. That means, if you finish dinner at 8pm, you wait until 10am to eat breakfast. On top of that, I now stick to my grandma’s advice and don’t snack, so I eat lunch at 2pm and dinner at 7pm. Each of those long breaks between meals gives me a tiny fast, and each meal, particularly lunch, feels huge to me. I hardly get hungry at all. In fact, back in the 70s and 80s, before the pundits told us all to eat all the time, I used to put off eating until I was really hungry and found that made it easier to lose weight. Some people would call that “skipping breakfast” and click their tongues, I just call it “breakfast”, literally the meal that breaks my fast.
Now for my progress on intermittent fasting… I seem to have plateaued at 55.2kg. Never mind, I’m sure that’s just temporary and I’ll be back to reporting losses again next week.
Clock image by Jean Scheijen