Rhonda: So there's one more area I kind of just wanted to touch on, mostly out of my own personal interests, and that is exercise timing and the circadian clock. There's been a bunch of studies that have come out over the past few years suggesting there are better times for humans to exercise.

Satchin: Yes. So there are a lot of studies that are coming out saying that by...so the late afternoon or evening may be the best time for exercise. And there are many physiological reasons for that. One is, for exercise, we need much better muscle tone, joint flexibility, and less risk for injury. And all of the stars align in the late afternoon because that's when our heart rate is relatively high, our core body temperature is warm. We don't need that warming up that we typically need early in the morning, that much warming up. And the muscle tone is better, joint flexibility is much better. So the risk for injury is less. So that's why all of the studies are finding that late afternoon exercise is much better. So this is for healthy people who are trying to get the gold medal instead of silver, reducing their risk for injury. Then if we think of people who are sick, or who are trying to manage their glucose, say, people with diabetes is late afternoon exercise better than early morning. And in fact, there is at least one study that came out of Stockholm showing that the same people, when they did exercise high-intensity interval training in the morning versus the same people doing the same high-intensity interval training in late afternoon, they found that people who did the morning, when they did the morning HIIT interval training, the blood glucose level actually went up, whereas doing the same exercise in the evening helped them to reduce their blood glucose level, 24 hours blood glucose to those who have diabetes. So that's a very strong result. And what we know is, as I said, our pancreas has a clock. That means the pancreas produces more insulin in the morning or the first half of the day. And the second half of the day, even in the absence of melatonin, it doesn't produce that much insulin as well as in the morning. So that means any help in managing glucose independent of insulin is much better in the evening. And when we exercise, our muscles actually take up a lot of glucose without the help of insulin. And this might be one reason why late afternoon, early evening exercise or even brisk walking may be much more beneficial for people with diabetes in managing their blood glucose. So the bottom line is, whether you're healthy or less healthy, it seems that late afternoon, early evening exercise is better. But at the same time, if you have time to exercise only in the morning, then you should not stop exercising. Go for that morning exercise.

Rhonda: Completely agree. There was a very interesting, very recent study showing that fat oxidation was about almost 13% higher in the afternoon compared to the morning. But if the participants took in...it was actually quite a large amount of caffeine, 30 minutes before exercise in the morning, their fat oxidation was equivalent to if someone exercised in the afternoon without any caffeine. So, for me, I like to exercise first thing in the morning, I'm sort of mostly fasted. I do have a cup of coffee. But it's kind of nice to know that maybe that caffeine...and I don't exactly know the mechanism, but may actually boost the fat oxidation a little bit more than if it was just morning without the caffeine. And also just one more question, there was another study showing that performance, athletic performance actually varied depending on when a person wakes up, so whether they're an early riser versus intermediate or late riser. And what I thought was so interesting about that study is that their peak performance was very different. So if it was an early or intermediate riser, your peak athletic performance happened between five or six hours after they wake up. But if they were a late riser, their peak performance was almost 12 hours, it's 11 hours after they basically woke up. So I thought that was 📍 interesting. 📍