Well, HIIT will not help build muscle. Unless we are talking about a completely sedentary individual whose most intense activity is walking up to the TV to change the channel.
And HIIT has no magical properties that will slow down aging. Essentially the main benefit of HIIT and fasting on anti-aging is helping you be in a caloric deficit and increasing AMPK release.
But HIIT isn’t necessarily any better in that regard than other forms of cardio.
I’m not gonna lie, it is hard to focus on both maximizing muscle growth and optimizing anti-aging as in a few regards both require different and even opposite physiological responses.
For example, muscle growth is optimized when you are in a caloric surplus, when. mTOR is activated more than AMPK and IGF-1 (and even insulin) are higher.
Anti-aging is best achieved when you are in a caloric deficit, when AMPK is activated more than mTOR and when IGF-1/insulin are lower.
That’s not to say that you cannot achieve some muscle growth while getting physiological anti-aging benefits. But you really cannot get the best of both world.
One approach that I like is the Primer 52 diet that I developed with Paul Carter.
Essentially you have 2 fasting days, 2 surplus/higher carb days, 2 low carb days (which can be in a deficit, at maintenance level or in a surplus depending on your goal) and one moderate day.
Physical activity is adjusted to the type of nutrition you are using on that day.
Now, one way that HIIT might potentially help with anti-aging, besides AMPK activation, is an increase in growth hormone production. This is maximized in very intense efforts lasting 30-60 seconds. That’s why I like the “Sprint 8” protocol. But:
- The transient increase in hGH will not make a HUGE impact
- You can get the same hGH release from resistance training that leads to a large lactate production.