Anti-aging with Coach Denys, Episode #5 – Exercise and Exposure to Cold Temperature

In the first 3 episodes of this podcast, I covered the what, why and how of aging, with the 2nd half of episode #3 being a seqway into more regimens and approaches to anti-aging. Episodes #3, #4 and #5 were dedicated to metabolic health, which is at the foundation of health and for staying away from chronic diseases. Episodes #3 and 4 focus on “how to adjust your diet” to improve your metabolic health.
In this episode #5, our topic switches to “how to adjust your lifestyle” toward the same goal (metabolic health), which is based on insulin sensitivity. We will cover two major areas in lifestyle: exercise and cold exposure.

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👇Scroll down for the 10 research papers and articles referenced in this episode and the complete transcript.

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1. Aerobic endurance exercise or circuit-type resistance training for individuals with impaired glucose tolerance? 

2.  Post-Exercise Carbohydrate-Energy Replacement Attenuates Insulin Sensitivity and Glucose Tolerance the Following Morning in Healthy Adults

3.  Pre- versus post-exercise protein intake has similar effects on muscular adaptations

4. Interventions for being active among individuals with diabetes: a systematic review of the literature 

5. Delivery of muscle-derived exosomal miRNAs induced by HIIT improves insulin sensitivity through down-regulation of hepatic FoxO1 in mice – (Proceedings of the National Academy of Sciences, 2020-11-16)

6. High-Intensity Interval Training Attenuates Insulin Resistance Induced by Sleep Deprivation in Healthy Males – PubMed, 2017-12-07

7. HIIT helps combat high insulin resistance — a warning sign for diabetes– Frontiers in Physiology, 2017-08-16

8.  Uncoupling protein 

9. Cold-induced brown adipose tissue activity alters plasma fatty acids and improves glucose metabolism in men. Iwen, K.A., et al., J Clin Endocrinol Metab, 2017.

10. High incidence of metabolically active brown adipose tissue in healthy adult humans: effects of cold exposure and adiposity, Saito, M., et al., Diabetes, 2009.


Hello, welcome to my podcast,  “Anti-aging with Coach Denys”, episode #5. Our topic today is: “Metabolic Health Part 3 – exercise and exposure to cold temperature.

On the highest level, simply put, among all the different ways to improve metabolic health, the most effective ones are in the two categories: proper diet and enough exercise. In the previous two episodes on the topic of metabolic health, I shared several fundamental guidelines for adjusting your diet; as to exercise, I introduced 3 simple ways in episode #3 for everyone to get started. That was only the basics though. In today’s episode, I am going to share with you more tips to optimize your workout routines aiming at improving your metabolic health, including the theories behind them. Toward the end, I will offer one additional modality other than diet and exercise for improving metabolic health.

In episode #3, I told you one of the major functions of insulin is to ensure that blood glucose level is maintained at a healthy level. Upon intake of any food, insulin kicks in to modulate the flux of glucose between your blood and your organ and muscle cells. One of the key modulation mechanisms it to determine how much of the glucose should be stored in the cells of your muscle and liver for short-term future use and how much should be converted and stored as fatty acids for relatively longer-term future use.

Keeping blood glucose level in check is critical – as any slight deviation could be fatal. This modulation task as owned by insulin is so critical that in the event when insulin is not keeping up with its job, one of our organs is uniquely granted the privilege to suck up glucose from the blood without permission (that is, signals) from the insulin. Want to make a guess which organ has such privilege? OK, I will give you a hint: it’s the the largest organ in size in human body. Some of you may say: ha, it’s the lung. Nope. The answer is: it’s our muscle. Yes, the muscle is considered an organ in physiology. That is to say, even if you have insulin resistance (or, more precisely, even if your muscle cells are resistant to the signals from insulin), as long as you have enough muscle cells and you use / contract your muscle, your muscle cells can absorb and use the glucose in the blood around without the help (instructions)  from the insulin, hence lower the glucose level in your blood.

Not just that, as long as you start moving and contract your muscle, even if the amount of your move and exercise is not high enough to cause any reduction in body weight, it still has the effect of improving your insulin sensitivity.

Exercise also has the benefits of 1. burning visceral fat, 2. reducing oxidative stress, and 3. lowering inflammation, the three contributors to insulin resistance.

Sounds pretty good, doesn’t it? Among those of you who are still with me thus far, some may already have the next question in mind: Toward the goal of improving insulin sensitivity, what type of exercises is more effective? For example, between aerobic exercise and anaerobic exercise, which is more effective?

That’s a great question and I will give you a comparison using three factors.

Factor 1: Time. If you have enough time, do both. If your time is enough only for one of the two, then weight training (anaerobic training) will give you better ROI (return on time investment) As a rough example based on my experience, a 60 minute resistance training or 15-minute HIIT can achieve an effect of maintain/enhance insulin sensitivity similar to a 2.5 to 3 hour aerobic exercise.

Factor 2: Muscle mass. The time duration your insulin stay sensitive after a workout is proportional to your muscle mass. In principle, weight training over time can increase your muscle mass (if done right and fed properly – a topic to be covered in details in episodes #8 and #9.) On the contrast, aerobic workout will not increase your muscle mass, period.

One common misconception about aerobic exercise is that although it can be quite effective for losing weight, losing weight does not equate to improved insulin sensitivity, at least not proportionally. This is because the weight loss from aerobic exercise always include both fat and muscle. In contrast, the weight loss from weight training (resistance training) tends to involve more fat than muscle (again, assume proper intake of protein pre- or post- training).

Hence, toward the goal of insulin sensitivity, anaerobic exercises such as resistance training and HIIT are tend to be more effective than aerobic exercises such as running, cycling and swimming. The key factor here is muscle mass.

Factor 3: Metabolic flexibility; that is, the degree of your body’s dependency on glucose as energy source.

So far my discussions on aerobic exercises has been quite general in the sense that I refer to them only as running, cycling, or swimming. With the notion of “metabolic health” in mind, I am going to introduce to you a unique technique in aerobic training that can give you two benefits that may sound too good to be true.

Benefit 1: you will never experience the so-called  “hitting the wall” in long-distance endurance races such as marathon or 100-km bike ride.

For those of you that never heard of it, “hitting the wall” refers to a state when an endurance athlete suddenly feels totally exhausted and has zero energy to move on. It typically happens at around 75 – 80% of a long distance endeavor such as a marathon. What’s significant here is this can happen to seasoned or even elite athletes. Newbies rarely experience it. Bottom line? The glucose level in the blood runs too low and the body is unable to switch to burning fat as energy source – that is the definition of “metabolic inflexibility”.

Benefit 2: You will be equipped with an optimal insulin sensitivity that lasts for months and becomes part of you instead of a hard-to-come-by glorious moment that stays with you for only an hour or two right after your 5K or 10K run.

So what do you do differently in your aerobic exercise to gain these two invaluable health benefits? Welcome to “Zone 2 training”. As the name suggests, you training should stay in “zone 2” of your heart rate. For starters, in all athletic training methods for aerobic exercise, heart rate is one of the key parameters to monitor. How heart rate affects the efficacy of your training and performance is beyond the scope of our discussion here. For our purpose in this episode, you only need to know the following: when monitoring an athlete’s heart rate, it is divided into 5 different zones. Zone 1 is the easiest, it’s the rate when you jog slowly or in a brisk walk, slightly higher than when you’re just walking. Typically between 85 and 105 beat per minute, depending on your age. At the other end of the spectrum is zone 5, which is when you are doing an all-out sprint, feeling breathless, and can stay in it for less than 20 or 15 seconds. Now, Zone 2 is the heart rate that is between zone 1 and zone 3. A simple formula goes like this: “180 minus your age is the lower end of your zone 2 heart rate”. For example, if you are 35, your zone 2 hear rate starts at (180 – 35 = 145 bpm). If you are 55, it starts at (180 – 55 = 125 bpm.) And so on… Your zone 2 heart rate is also called your “aerobic heart rate”.

To gain the two benefits I mentioned above, that is, say goodbye to “hitting the wall” and “achieve optimal insulin sensitivity for long-term”, here are some guidelines and tips regarding zone 2 training:

Train at or around your zone 2 heart rate for at least 40 minutes each time, ideally 1 hour or longer. The benefits start to diminish when exceeding 2 hours.

Do zone 2 training at least twice a week, ideally 3 or 4 times a week.

Other than water with electrolytes, no food intake before and during the exercise. If you do the zone-2 training after a 12 to 16 hour fasting, you will see the efficacy sooner (I.e., after a few weeks instead of months).

The exercise can be in any form of movement, running, swimming, or cycling or even just walking. The key is: you must keep your heart rate in zone 2 as defined by the formal above.

Depending on other factors including diet, sleep, and stress, in general, you will start to see the benefits after maybe one month, more likely it will take 2 months. The longer each session and the more frequently you do it (ideally 3+ times a week), the sooner you will see the change.

That’s the theory and the method. Now Im going to share with you a practical tip based on my experience. It may sound like such training method requires wearing a heart rate monitor on your chest or wrist and you have to keep an eye on your heart rate at all time during your exercise. Practically speaking, that’s how you should do it when you first try it. After a while, you will get a sense about whether your HR is in Zone 2 without staring at your Apple or Garmin watch at all time. Here is how: Let’s use running as an example and you are running with a partner. You know you reach your zone-2 heart rate when you can run at the fastest pace while maintaining a conversation with your partner. Slightly faster, you can no longer maintain the conversation. That’s when your HR is in zone 2.

When it comes to improving insulin sensitivity, zone 2 training is like a double-edged sword. On one edge, it cuts fat. On the other edge, it makes you less dependent on glucose as source of energy. It has been proved in medical research that too much reliance on glucose for energy has a high association with insulin resistance. We are not sure which of the two is the cause. But that’s not important. As you training in zone two, over time, the following two conditions will happen at the same time – condition 1: you can train with less or even zero carb, and condition 2: you can skip a meal easily during a rest (no training) day. One downside of zone-2 training is that it’s time-consuming, like most truly valuable things in life, there is no shortcut. Another down side is that it doesn’t help with MPS (muscle protein synthesis), although it won’t cause MPB either.

Another important guideline about zone-2 training for insulin sensitivity is that avoiding food intake (especially carb) in the 1 to 2 hours post training can further enhance the efficacy of enhancing insulin sensitivity. You heard that correctly. Post-workout nutrition intake reduces the efficacy of insulin sensitivity improvement, if that is your purpose of the workout. There is a 2018 research report on PubMed on this topic. It’s based on a randomized control trial. Link to the article will be in the show notes. (Ref. 2)

“So, how long should I wait after a zone-2 training session before I eat?” you may ask. The answer is: the longer the better, if your goal is to improve your insulin sensitivity. In real life tough, very few of us live our days for one single purpose. We all have other tasks or objectives to pursue that are either physically demanding (say, you have a weight training session in a few hours) or mentally taxing (maybe you are presenting a project to your boss at work). So in most cases you will want to refeed in time.

Now, for the sake of learning let’s get a bit geekier and dive deeper. Let me expand the scenario from just a zone-2 training to a more anaerobic resistance training or HIIT. For the goal of insulin sensitivity, anaerobic training is less effective than zone-2 training. That said, you would still benefit from an improved insulin sensitivity if you avoid food intake right after the anaerobic training. That brings up a different issue: resistance training or HIIT always cause some MPB. So wouldn’t it make sense to trade off some insulin sensitivity with protein refeed right after the workout to promote MPS and avoid MPB? Here is another surprise: recent researches have shown that, as long as the quality and amount of protein intake are the same, you do not need to refeed right after a resistance training to achieve a better MPS. As long as the refeed is within 24 hours after the workout, the effect of MPS is about the same. That is to say: the so-called “post-workout anabolic window” is not 30 or 60 minutes post workout as most of us have been told in the past decades. The window is 24 hours. In the show notes you can find the link to a 2017 research report on PubMed on this topic. That said, I have recently heard some experts say that the extended “post-workout anabolic window” of 24 hours works only for people who have been doing resistance training consistently for several months. For beginners, the window may be much shorter than 24 hours.

One reminder here about zone-2 training is that you have to be disciplined. Your heart rate must stay in zone-2 for the majority of your training session. It may sound easy and yet it’s harder than you think. Most people engaging in aerobic training (especially running) tend to escalate their HR into zone 3 or zone 4, knowingly or unknowingly. It really takes disciplines to stay in zone 2. Here, your ego is your enemy. The more seasoned and passionate you are into running, the more likely you will make such mistake.

Let me do a quick recap here. What I have shared on what and how to exercise so far are based on 3 major factors or actionable triggers:

Body composition – the more muscle mass the better, you want to reduce fat, especially visceral fat.

Move your body, use your muscle. Doing so can help your body not just burn fat but also reduce oxidative stress and lower inflammation.

Teach your body to burn fat; that is, enhance your “metabolic flexibility”.

Now I am going to introduce a 4th factor or trigger you can act on: The intensity of your workout. In principle, everything being equal, workout with higher intensity is more effective in improving your insulin sensitivity. (Ref. 4, Ref. 5, Ref. 6, Ref. 7) But wait, what do we mean by “intensity” here? First, the intensity of a workout is not the same as the volume of a workout. Let’s say you spent 35 minutes to run 5 km at a pace of 7:00/km. The volume isn’t insignificant. But the intensity is pretty low. On the contrast, if you spent 1 minute to run 400 meters, the volume is insignificant but the intensity is quite high – close to that of an elite sprinter! Of course, whether a workout is considered high intensity has to do with the individual’s age and fitness level. A running pace of 7:00/km is considered low intensity for someone at 25 but high intensity for someone who is 80-year old or never run more than a few hundred meters in life.

That’s a brief explanation of intensity. To define intensity scientifically, typically two metrics are used: heart rate and the level of lactate acid in muscle cells. As intensity goes up, the two numbers also go up. While you can easily measure your heart rate, measuring  lactate acid requires special equipment. For most of us who are not pro-athletes under some costly training program pursuing advancements that require precision measurement, especially for our topic of insulin sensitivity here (instead of sports performance), we can just use “perceived level of exertion” to measure the intensity. That’s more than enough. The more physical pain (or uncomfortable feeling) and the shorter you can sustain, the higher intensity your workout has reached. Now I am going to share some practical tips to reach high intensity in running, cycling, and resistance training.

Before I proceed, let me remind you that it’s an N=1 sharing based on my experience. Before you decide to adopt it, you should consult your medical doctor first to decide if these tips are safe for your current physical condition.

Regardless of types of exercise, my first tip for your approach to reaching high intensity may sound unconventional: “Go big or go home” is better than “progressive overload”. The key here is: the duration has to be very short. If it’s not very short, first it may cause damage to your body, secondly the intensity is probably not high enough. Welcome to the now highly popular term of HIIT, High Intensity Interval Training. Here is how…

Running: Try sprinting with an all-out dash of 100 meters. It should take most of you between age 25 and 55 anywhere from 13 to 18 seconds. If your fitness level is average and it takes you more than 22 seconds, it’s probably not an all-out for you. Try running faster. You know it’s an all-out when you feel your heart was about to pop, your skeleton about to collapse, or your ab about to cramp in the last 2 seconds of your dash. A few important notes:

Before you try it, it is critically important to warm up with a zone-2 run of at least 15 minutes first.

Dash at least 4 times but no more than 7 times.

Take a 1-minute rest between each dash. Older people can take a longer rest but try not to exceed 3 minutes.

On the following day, expect to feel more tired (though not more soreness) than running a 10 K in zone 2.

Cycling: Use your max power to ride up-hill in an off-saddle sprint (a.k.a. dancing). If you can do so for more than 15 seconds, your output wattage is probably not high enough. Try a steeper hill or shift to a higher gear. Slow down for a 1 to 2 minute break after each up-hill sprint. Repeat for 5 to 6 times.

Resistance training: With a load that you can push or lift for 15 to 20 repeats in one set, warm up with 3 to 5 sets.  Take a few minutes’ rest and switch to a load that you can do only 4 to 8 repeats in one set. With the increased load, do 3 to 5 sets. Take a 3 minute rest between each set. In the post-warm up stage, if you can do more than 8 push/lifts, it’s not heavy enough and you should increase the weight. Your should be able to do only 3 or 5 push/lifts in your last set and feeling barely make it with your last push. Important reminder here: when trying HIIT in resistance training, you are strongly advised to always have a partner as your “spotter” next to you for safety consideration.

The benefits of HIIT goes beyond enhancing insulin sensitivity, including strengthening your mitochondria, which fundamentally impact all aspects of your health and eventually your longevity.

One last note: While HIIT helps maintain and enhance your insulin sensitivity, for optimizing metabolic flexibility, that is, the ability to rely mostly on fat as energy source for extended period (24+ hours or days of fasting), zone-2 training is more effective than HIIT. But, to get to such flexibility with zone-2 training it usually takes at least 2 months, more likely 4 or 6 months.

In the last part of this episode, let me share another way to improve your metabolic health. It’s not another type of exercise although it has a similar effect. Welcome to “cold exposure”.

To help you understand how it works, I need to introduce two special kinds of fat tissues in human body: brown adipose tissues and white adipose tissues, abbreviated as BAT and WAT.

Most of us have seen the fat tissues in the animal meat in our food, fats are mostly white in color. Fat tissues in human body isn’t that much different. Most of the fat tissues in our body are “white adipose Tissues”. Only a very small portion of our fat tissues are Brown Adipose Tissues. What makes the BAT appear brown is the mitochondria in it. The color of mitochondria, as seen under microscope, is dark reddish or brown. BAT contains way more mitochondria than WAT. WAT contains almost zero mitochondria.

As I have discussed in previous episodes, mitochondria are the tiny yet critical “power plants” around all cells in our body, with the only exception of red blood cells. Without mitochondria, human being as a form of life will stop and die immediately. Actually this is true for all eukaryotic cells (cells with clearly defined nuclei). In performing such critical and fundamental function, mitochondria follow a rule: they provide energy in the form of ATP (Adenosine Triphosphate) only when its “mother cell” needs energy. There is only one exception: mitochondria in BAT are exempt from this rule. Even when their “mother cells” do not need energy, mitochondria around BAT cells can take the glucose nearby to generate ATP. Such exception can happen only under one condition, which I will tell you in just a moment. Energy generated by mitochondria in such condition is not to be used by their mother cell. Instead, the energy is used to generate heat, which gets dissipated around. This effectively prevents the glucose level from staying too high for too long, effectively helps maintain insulin sensitivity.

Such unique function of mitochondria in BAT is enabled by a special protein present only in the inner membrane of BAT called “uncoupling protein”. While WAT store glucose into fat cells, BAT by contrast convert glucose into energy (that is, heat). In this regard, BAT function almost the same way as muscle tissues.

Now, what is that “one condition” I mentioned earlier to allow such “magic” to happen in BAT? When BAT is exposed to temperature at or below 65 degree Fahrenheit (18 degree Celsius). This number, 65 degree Fahrenheit is based on solid science. I will leave links to 2 research papers in the show notes. (Ref. 9 & 10).

To enhance insulin sensitivity, what I have shared in this episode include proper diet, enough exercise, and exposure to cold temperature. 65 degree F may sound pretty cld, especially for those of you in Taiwan or southeast Asia. But it’s not too cold an environment to endure or create, as I will share momentarily. So, that’s a good news. The bad news is: human body has very limited amount of BAT, found only in a few small areas on our body. They are mostly found in the lower neck and the area above the collarbone. A small amount is scattered around the hard organs in the chest. Translated into practical application, this means when you deliberately try to expose your BAT to such low temperature (by submerging in cold water or taking a cold water shower) you want to aim the exposure at your neck and the areas around your collarbone.

How long should each cold exposure session last for it to be effective in enhancing insulin sensitivity? Good news is it doesn’t need to be too long. Even a 1-minute session can be beneficial. The longer the better, although the efficacy starts to diminish after 15 minutes. Beginners can start with a shorter session of 30 seconds to 1 minutes at a higher temperature of, say, 72 degree. Extend the session to 1+ minute at temperature inching closer to 65 F in 1 to 2 weeks if you try it once a day. Time of the day doesn’t matter, although doing it after wakeup has an additional benefit of boosting your cortisol hence dopamine to facilitate a healthier circadian rhythm – an important topic in anti-aging and health in general in future episodes.

Before I end episode #5, allow me to offer you a refresher and overview on what I have covered in the 5 episodes so far. In the first 3 episodes I covered the what, why and how of aging, with the 2nd half of episode #3 being a seqway into more regimens and approaches to anti-aging. Episodes #3, 4 and 5 were dedicated to “metabolic health”, which is at the foundation of health and for staying away from chronic diseases. Episodes #3 and 4 focus on “how to adjust your diet” to improve your metabolic health. Episode #5, our topic today, switches to “how to adjust your lifestyle” toward the same goal, which is based on “insulin sensitivity”. We covered two major areas in lifestyle: exercise and cold exposure. Exercise itself is a topic that deserves many episodes to elaborate, including the how & why behind different types of exercise, recovery, nutrition plan, injury prevention, and performance – and that’s just a partial list. My sharing on exercise today is just to get you started. Now let’s bring our focus back to insulin sensitivity. Let’s take a “hormone perspective” to summarize our learning today and have a peek into what else on the horizon are waiting for us to explore for an optimized insulin and metabolic health – after all, insulin is part of our hormone system.

From a hormone perspective, there are mainly three triggers for insulin resistance:

Extended elevation of insulin level.

Too much stress in life. High stress over-drives cortisol, hence impacts proper functions of adrenaline and insulin.)

Too much inflammation (It involves several hormones including gluco-corticoid, thyroid, estrogens, progesterone and testosterone.)

What episodes #3, 4 and 5 cover are ways to contain the 1st trigger. Containing the 2nd and 3rd triggers tend to be much more multi-factorial. The efficacy is also harder to quantify. For sure we will discuss these 2 triggers, stress and inflammation more in depth in future episodes although the concern will not be solely for insulin sensitivity.

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