#96 How to Improve Metabolic Health with HIIT, Circadian-Timed Eating, & Sleep

Posted on October 10th 2024 (6 months)

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Exercise, meal timing, and sleep. What do they have in common? They’re the foundation of a healthy lifestyle. I also consider them to be straightforward areas to tackle when it comes to longevity strategies. They do require effort to implement, but doing so is incredibly simple.

The good news is that because there are several levers to pull, we don't have to choose just one. But we do need to be diligent about taking action to support our longevity. This begins with optimizing our metabolic health.

Metabolic health has ramifications that extend far and wide. Our body’s ability to regulate blood glucose levels stands out as one of the most important metrics predicting long-term health.

Even having high plasma glucose levels that fall within the normal range is associated with greater atrophy of the hippocampus and amygdala—two structures in the brain with relevance to aging and neurodegenerative processes. Having a high HbA1c, which is considered a long-term marker of glucose regulation, leads to the formation of advanced glycation end products or AGEs. AGEs can crosslink with protein and lipids, including collagen, reduce the elasticity of our heart and contribute to a stiffening of blood vessels, and promote high blood pressure, putting us at risk for cardiovascular disease.

It’s clear that we should be doing all that we can to improve our metabolic function throughout life.

Recently, I gave a talk at the American Academy of Anti-Aging Medicine (A4M) conference in Palm Beach, Florida where I presented my top three strategies for optimizing metabolic health:

  • High-intensity interval training (HIIT)
  • Circadian-timed eating
  • Quality sleep

Some highlights from this episode:

  • Why HIIT outshines moderate-intensity exercise for improving metabolic health
  • How lactate accumulation from higher training intensity benefits glucose homeostasis
  • The optimal HIIT conditions for improving body composition
  • How vigorous exercise boosts mitochondrial repair through mitophagy
  • Evidence-based HIIT protocols (Tabata, Wingate, 1-minute on/1-minute off, and Norwegian 4x4)
  • Just 10 reps of this exercise every 45 minutes is more powerful at improving glucose homeostasis than a 30-minute walk
  • How to improve postprandial glucose regulation with "exercise snacks"
  • Why it's beneficial to time meals with melatonin release
  • Can high-normal glucose levels shrink your hippocampus?
  • How even mild sleep restriction creates a metabolic profile similar to type 2 diabetes
  • Why just 1 hour of extra sleep might help you lose weight
  • How to ameliorate the increased mortality risk associated with sleeping less than 7 hours a night

High-intensity interval training (HIIT)

“HIIT provides an opportunity for people to have a time-efficient way for improving their metabolic health.” - Dr. Rhonda Patrick Click To Tweet

HIIT is a time-efficient training technique that involves short, intense bursts of physical activity alternated with brief recovery periods or light exercise. The metabolic benefits of HIIT include:

  • Improved triglycerides and glucose regulation
  • Increased insulin sensitivity
  • Decreased fat mass and improved body composition
  • Enhanced mitochondrial function

HIIT outperforms moderate-intensity continuous exercise, leading to greater improvements in:

  • Cardiorespiratory fitness (e.g., VO2 max)
  • Systolic and diastolic blood pressure
  • High-density lipoproteins
  • Triglycerides
  • Fasting blood glucose
  • Oxidative stress and inflammation
  • Appetite-regulating hormones and beta-cell function
  • Markers of mitochondrial biogenesis
  • Cardiac function

What explains the unique benefits of HIIT?

During high-intensity exercise, our mitochondria and muscles undergo a significant energetic stress—our body can’t keep up with energy production via fat metabolism alone, so our body switches to using glucose and glycogen (glycolysis) for ATP production. In the process of breaking down glucose, lactate is produced. Rather than a toxic byproduct, lactate can be used as a source of energy for the body and the brain.

But that’s not all, lactate is also a potent signaling molecule that allows for cross-talk between our muscles and other organs throughout the body. Among its other signaling effects, lactate increases GLUT4 transporters in skeletal muscle, allowing for a greater amount of glucose uptake. This effect lasts for up to 48 hours, with the first 24 hours representing the most robust period of enhanced glucose control.

The optimal HIIT protocol to improve body composition

High-intensity training reduces fat mass and body fat percentage and increases fat-free mass (i.e., lean body mass). Running and cycling HIIT protocols appear to be the most effective, especially when the following parameters are adhered to:

  • Duration: More than 8 weeks of training
  • Frequency: At least 3 sessions per week
  • Interval structure: Less than 60 seconds per interval with 90 seconds or less of active recovery

HIIT corrects mitochondrial dysfunction in type 2 diabetes

“Lactate is consumed by other organs…and it’s serving as a very utilizable source of energy. But one of its most important roles is as a signaling molecule.” - Dr. Rhonda Patrick Click To Tweet

People with type 2 diabetes demonstrate markers of mitochondrial dysfunction, characterized by 40% lower mitochondrial respiration and enlarged, fragmented mitochondria, indicative of mitochondrial damage. These structural and functional changes are correlated with insulin resistance.

High-intensity exercise increases a cellular repair process known as mitophagy—it sends a signal to clear out and recycle damaged or dysfunctional mitochondria. In this way, long-term exercise training leads to more and healthier mitochondria. Mitophagy is a similar process to autophagy, which is enhanced during intermittent fasting or periods of low energy availability. But exercise appears to be a much more robust signal for mitophagy than fasting. In fact, exercise enhances mitophagy whether or not it’s performed in the fasted state.

HIIT also enhances mitochondrial biogenesis in skeletal muscle in addition to increasing the effectiveness and efficiency of existing mitochondria. This is the result of the potent effects of lactate, which send a signal to the body to increase mitochondria as an adaptation to produce more energy.

Other metabolic benefits of HIIT occur through increasing a muscle protein called PGC-1α. Higher levels of PGC-1α can improve muscle's oxygen use, antioxidant defense, and glucose management, and may also protect against muscle loss with aging and reduce inflammation.

HIIT protocols to improve metabolic health

  • Tabata training: Tabata training involves performing 8 intervals total alternating between 20 seconds at 170%+ of VO2 max and 10 seconds of rest. Not including the warmup and cooldown, this workout takes 4 minutes to complete.
  • Wingate intervals: Wingate training, named for the exercise test for which this workout was named, involves performing 4–6 intervals total. The hard portion is 30 seconds at an “all out” intensity followed by 4 minutes of rest or active recovery. Not including a warmup and cooldown, this workout takes 18–27 minutes to complete.
  • 1-minute on/1-minute off training: This protocol involves performing 10 intervals total alternating between 60 seconds at 90%+ of heart rate reserve and 60 seconds of rest or active recovery. Not including a warmup and cooldown, this workout takes 20 minutes to complete.
  • Norwegian 4x4 training: Named because it’s performed by the Norwegian ski teams, this workout involves performing a total of 4 intervals alternating between 4 minutes at 85–95% of maximal heart rate and 3 minutes at 60–70% of maximal heart rate. Not including a warmup and cooldown, this workout takes 25 minutes to complete.

Exercise snacks to improve metabolic health

Exercise snacks are brief bouts of high-intensity exercise (75% or more of maximum heart rate) performed intermittently throughout the day for 1–2 minutes.

Examples of exercise snacks include:

  • High knees
  • Lunges
  • Stair sprinting
  • Jump squats
  • Chair squats

Strategically timing exercise snacks 30–60 minutes before or after meals appears to markedly improve glucose regulation, regardless of whether or not someone has insulin resistance.

Exercise snacks also improve longevity: People who engage in ~3 bouts of exercise snacks/vigorous intermittent lifestyle physical activity (VILPA) per day (each lasting 1–2 minutes) have a 40–50% reduction in all-cause, cancer, and cardiovascular disease mortality compared to people who don’t engage in exercise snacks.

Circadian-timed eating

“People that do early time-restricted eating without reducing their calorie intake dramatically improve a variety of metabolic parameters.” - Dr. Rhonda Patrick Click To Tweet

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