 Welcome to the Nutrition Facts Podcast. I'm your host, Dr. Michael Greger. The coronavirus pandemic has made many people Michael Greger. They are the importance of maintaining and improving our health. Make that your silver lining. Because the more positive change we can make to our diet and lifestyle, the better. There's been a lot of research lately on the best and safest way to boost our metabolism. And here's a sample of what we found. In our first story, we look at how our adrenaline system plays a role in regulating our metabolism and our weight. Thermogenic drugs like DMP can cause people to overheat to death, can increase resting metabolic rates by 300% or more. A more physiological spread would range about 10 times less, from a 30% slower metabolism in people with an underactive thyroid to a 30% higher metabolism when the part of our nervous system that controls our fight or flight response is activated. In response to a fright or acute stress, special nerves release a chemical called noradrenaline to ready us for confrontation. You experience that by your skin getting paler, cold, and clammy as blood is diverted to your more vital organs, your mouth can get dry as your digestive system is put on hold, your heart starts to beat faster. What you don't feel is the extra fat being burned to liberate energy for the fight. That's why people started taking ephedra for weight loss. Ephedra is an evergreen shrub used for thousands of years in China to treat asthma, because it causes the same release of noradrenaline that offers relief to asthmatics by dilating their airways. In the United States, it was appropriated for use as a metabolic stimulant, shown to result in about two pounds of weight loss a month in 19 placebo-controlled trials. By the late 1990s, millions of Americans were taking it. The problem is that it had all the other noradrenaline effects like increasing heart rate and blood pressure, and so chronic use resulted in strokes, heart arrhythmias, and death. The FDA warned the public of the risks in 1994, but it wasn't banned until a decade later after a major league pitcher dropped dead. In the current wild west of dietary supplement recommendation, a supplement can be marketed without any safety data at all, and the manufacturer is under no obligation to disclose adverse effects that may arise. No surprise, then, that online vendors assured absolute safety, no negative side effects, 100% safe for long-term use. The president of Metabolife International, leading seller of ephedra, assured the FDA that the company had never received a single notice from a consumer that any serious adverse health event had occurred. In reality, they received 13,000 health complaints, including reports of serious injuries, hospitalizations, and deaths. If only there was a way to get the benefits of ephedra without the risks. There is, but to understand, you first have to grasp a remarkable biological phenomenon known as the diving reflex. Imagine yourself walking across a frozen lake and suddenly falling through the ice, plunging into the icy depths. I'm starting to think about greater instant fight-or-flight shock than that. Indeed, no adrenaline would be released, causing the blood vessels in your arms and legs to constrict to bring blood back to your core. You can imagine how fast your heart might start racing, but that would actually be counterproductive, because you'd use up your oxygen faster. Remarkably, what happens instead is your heart rate actually slows down. That's the diving reflex. First described in the 1700s, air-breathing animals are born with this automatic safety feature to help keep us from drowning. In medicine, we can exploit this physiological quirk with what's called a cold face test. To see if a comatose patient has intact neural pathways, you can apply cold compresses to their face to see if their heart immediately starts slowing down. Or, more dramatically, it can be used to treat people who flip into an abnormally rapid heart rate. Remember that episode of ER where Carter dunks the guy's face into a tray of ice water? And it was on TV when I was in medical school and a group of us would gather around and count how many times they violated universal precautions. Okay, but what does this have to do with weight loss? The problem with noradrenaline releasing drugs like ephedra is the accompanying rise in heart rate and blood pressure. But what the diving reflex shows is that it's possible to experience selective noradrenaline effects raising the possibility that there may be a way to get the metabolic boost without risking stroking out. Unbelievably, this intricate physiological feat may be accomplished by the most simplest of acts instead of drowning in water, simply drinking it. Wait, what? You can boost your metabolism drinking water? Buckle your safety belts. You are in for a wild ride. In our next story, we discover the effect of drinking water on adrenal hormones. Drink a few cups of water, and within three minutes, the level of the adrenal gland hormone noradrenaline in your bloodstream can shoot up. 60%. Have people drink two cups of water with electrodes stuck in their legs, and within 20 minutes, you can document about a 40% increase in bursts of fight-or-flight nerve activity. Chug two or three cups of water, and blood flow squeezes down in your calves and arms, clamping down nearly in half as arteries to your limbs and skin constrict took divert blood to your core. That's why, for example, drinking water can be such a safe, simple, effective way to prevent yourself from fainting, known medically as syncope. Fainting is the sudden, brief loss of consciousness caused by diminished blood flow to your brain. About one in five people experience this, at least one, one in ten may have repeated episodes, causing millions of emergency room visits and hospitalizations every year. Though fainting can be caused by heart problems, it is most often triggered by prolonged standing because blood pools in your legs or strong emotions, which can cause your blood pressure to bottom out. About one in 25 people have what's called blood injury or injection phobia. We're getting a needle stick, for example, can cause you to faint. More than 150,000 people experience fainting or near fainting spells each year when they donate blood. All you have to do to help prevent yourself from getting woozy, though, is just chug two cups of water five minutes before getting stuck. The secret isn't bolstering your overall blood volume. I mean, drinking two cups of water, even a whole quart, and your blood volume doesn't change more than, like, one or two percent. It's due rather to the shift in the distribution of blood towards your center, caused by the noradrenaline-induced peripheral artery constriction. Water drinking stimulates as much noradrenaline release as drinking a couple cups of coffee or smoking a couple unfiltered cigarettes. If the simple act of drinking water causes such a profound fight-or-flight reaction, why doesn't it cause our heart to pound and shoot our blood pressure through the roof? It's like the diving reflex I talked about in the last video. When we drink water, our body simultaneously sends signals to our heart to slow it down to still your beating heart. You can try it at home and measure your heart rate before and after drinking two cups of water. Within 10 minutes, your heart rate should slow by about 4 beats per minute, and by 15 minutes, you should be down 6 or 7 beats. One of the ways scientists figured this out is by studying heart transplant patients. When you move a heart from one person to another, you have to sever all the attached nerves. Amazingly, some of the nerves grow back, but still give healed heart transplant patients two glasses of water, and their blood pressure goes up as much as 29 points. The body is unable to sufficiently quell the effect of that burst of noradrenaline. Some people have a condition known as autonomic failure, in which blood pressure regulation nerves don't work properly, and their pressures can dangerously skyrocket over 100 points after chugging two cups of water. That's how powerful an effect the simple act of drinking a glass of water can be, and the only reason it doesn't happen to all of us is that we have an even more powerful counter-response to keep our heart in check. It reminds me of the poor woman who had a stroke after taking the ice bucket challenge due to an insufficient diving reflex to tamp down all that extra noradrenaline release. The remarkable water effect can be useful for people suffering from milder forms of autonomic failure, such as orthostatic hypotension, which is when people get dizzy standing up suddenly. Drinking some water before getting out of bed in the morning can be a big help. But what about that metabolic boost with so much noradrenaline being released with your adrenal gland hormones and overdrive? Might drinking a few glasses of water cause you to burn more body fat, could tap water, be like a safe form of a fedrum, all the weight loss with a nice slowing of your heart rate instead. Researchers decided to put it to the test, which we'll explore next. Given the 60% surge in the adrenal hormone noradrenaline within minutes of just drinking two cups of plain water, might one get the weight loss benefits of noradrenaline releasing drugs like a fedrum without the risks? You don't know until you put it to the test. Published in the Journal of the Endocrine Society, the results were described as uniquely spectacular. Drinking two cups of water increased the metabolic rate of men and women by 30%. The increase started within 10 minutes and reached a maximum within an hour. In the 90 minutes, after drinking a single tall glass of water in the study, subjects burned about an extra 25 calories. Do that four times a day throughout the day, and you could wipe out 100 extra calories, more than a fedrum. You'd trim off more calories drinking water than taking weight loss doses of the banned substance effedrin, the active component of a fedrum, three times a day. And we're just talking about plain, cheap, safe, and legal tap water. Using the 10 calorie rule, I explained previously, unless we somehow compensated by eating more or moving less, drinking that much water could make us lose 10 pounds over time. In essence, concluded one research team, drinking water provides negative calories. A similar effect was found in overweight and obese children. Drinking about two cups of water led to a 25% increase in metabolic rate within 24 minutes, lasting at least 66 minutes until the experiment ended. So just getting the recommended daily adequate intake of water, about 7 cups a day for children ages 4 through 8, and for ages 9 through 13, 8 cups a day for girls and 10 cups for boys, may offer more than just hydration benefits. Not all research teams were able to replicate these findings, though. Others only found about a 10 to 20% increase, 5% increase, or effectively, none at all. Pouring cold water, one might say, on the whole concept. What we care about, though, is weight loss. The proof is in the pudding. Let's test the waters, shall we? Some researchers suggest the increase in metabolic rate with water drinking could be systematically applied in the prevention of weight gain. Talk about a safe, simple, side-effect-free solution. In fact, free in every sense. Drug companies may spend billions getting a new drug to market. Surely a little could be spared to test something that, and at the very least, couldn't hurt. That's the problem. The water is a cost-free intervention. There are observational studies suggesting that those who drink, for example, 4 more cups of water a day, appear to lose more weight independent of confounding factors, such as less soda or more exercise. But you don't really know until you put it to the test. And finally, in 2013, effective water-induced thermogenesis on body weight, body mass index, and body composition of overweight subjects. 50 overweight girls, actually women, ages 18 to 23, were asked to drink 2 cups of water 3 times a day, half an hour before meals, over and above their regular water intake, without otherwise changing their diets of physical activity, and they lost an average of 3 pounds in 8 weeks. What happened to those in the control group? There was no control group, a fatal flaw for any weight loss study, due to the Hawthorne effect. We're just knowing you're being washed and weighed may suddenly affect people's behavior. Of course, we're just talking about water, so with no downsides, one might as well give it a try, but I'd feel more confident if there were some randomized controlled trials to really put it to the test. Thankfully, there are. I hate it when the title ruins the suspense. Overweight and obese men and women randomized to 2 cups of water before each meal lost nearly 5 pounds more body fat in 12 weeks than those in the control group. Both groups were put on the same calorie restricted diet, but the one with the added water lost weight 44% faster. A similar randomized controlled trial found that about 1 in 4 and the water group lost more than 5% of their body weight compared to only 1 in 20 in the control group. The average weight loss difference was only about 3 pounds, but those who claimed to have actually complied with the three times a day instructions lost about 8 more pounds compared to those who only did the extra water once a day or less. This is comparable to commercial weight loss programs like Weight Watchers, and all they did was drink some extra water. We would love it if you could share with us your stories about reinventing your health through evidence-based nutrition. Go to nutritionfacts.org slash testimonials. We may share it on our social media to help inspire others. To see any graphs, charts, graphics, images, or studies mentioned here, please go to the Nutrition Facts podcast landing page. There you'll find all the detailed information you need, plus links to all the sources we cite for each of these topics. For vital, timely texts on the pathogens that cause pandemics, you can order the e-book, audio book, or now hard copy of my latest book, How to Survive a Pandemic. For recipes, pre-order my How Not to Diet Cookbook out this December. It's beautifully designed, with more than 100 recipes for delicious and nutritious meals. And all proceeds I receive from the sales of my books go to charity. NutritionFacts.org is a non-profit science-based public service where you can sign up for free daily updates and the latest in nutrition research via bite-sized videos and articles. Everything on the website is free. There's no ads, no corporate sponsorship. It's strictly non-commercial, not sign anything. I just put it up as a public service, as a labor of love as a tribute to my grandmother, whose own life was saved with evidence-based nutrition.