Boost Metabolism With Interval Training

Age and Metabolism

It’s definitely not your imagination! As we age, our metabolism changes. A combination of factors contributes to create a perfect storm.

Before I get into the details, I’d like to announce that this blog is an excerpt of a course that will be available in the brand new community (and business) that myself and a Co-Founder have created. Our launch date will be August 29th, 2024. This is the reason I’ve been delayed on my personal newsletters, and the reason (if you know me personally) that I have been M.I.A. 🙂

Let’s get back into age and metabolism!

Some of the reasons our metabolism changes as we age include:
1. Stress and Cortisol:
When we are stressed for long periods of time, our cortisol levels can spike.
Elevated cortisol is linked to:
weight gain
high blood pressure
fatigue
changes in mood
irritability
flushed face
thinning skin
difficulty concentrating
insulin resistance

2. Loss of Fast Twitch Fibers:
Aging typically leads to a decrease in the number and size of fast twitch muscle fibers, which can contribute to reduced strength, power, and metabolic rate. With fewer fast twitch fibers, metabolism may slow down, making weight management more challenging unless targeted exercises are employed to maintain or even enhance these fibers. VERY few healthcare professionals, and even personal trainers mention this, but I’ve seen first hand how this is an enormous factor. Don’t worry, we’re going to explain what the heck these are in this lesson. 🙂

3. Lack of Sleep:
One study in JAMA mentions something we know to be true: when we don’t sleep well, we gain weight. It’s a recipe for issues.
People who sleep less:
–crave fattier foods
–see a spike in blood pressure
–have decreased Leptin levels, which means you don’t feel as full (even if you are), which means you eat more
–have increased Ghrelin levels which makes you feel hungry

It’s so important to try to manage our stress, get enough sleep, and understand the changes in our body as a baseline.

muscle fibers and metabolism, the secret link

Your Muscle Fiber Type Matters

Here are a few of the things that happen to our muscles as we get older:
Reduction in Muscle Fiber Size and Number: Muscle Atrophy: Aging is associated with sarcopenia, a condition characterized by the loss of muscle mass and strength.
Fast Twitch Fiber Vulnerability: Fast twitch muscle fibers are particularly vulnerable to atrophy compared to slow twitch fibers due to their reliance on anaerobic metabolism and higher energy demands.
Loss of Motor Units: Motor units (a motor neuron and all the muscle fibers it innervates) that control fast twitch fibers can decrease in number with age, further contributing to muscle weakness and reduced power output.
Changes in Muscle Composition:Shift Towards Slow Twitch Fibers: There is evidence suggesting that aging leads to a shift in muscle fiber composition, with a relative increase in slow twitch fibers and a decrease in fast twitch fibers.
Impact on Performance: This shift can impair explosive movements, decrease speed, and reduce the ability to generate quick bursts of force needed for activities like climbing stairs, lifting heavy objects, or even maintaining balance.

This will be a vast over simplification since there are many different types of muscle fibers, but for practical purposes we’ll discuss the key types (and then get into why it matters!!). Muscle fiber type is heavily influenced by the aging process. The percentage of type II “fast twitch” muscle fibers tend to decline with age. The way our muscles behave in general also changes as we age.

Muscle Fiber Types: Muscle fibers are categorized into two main types based on their contraction speed, endurance, and metabolic pathways. Everybody has a mix of all muscle fiber types. However, we typically have more of one type overall in our teens and early adult years. Here are the types (again, a simplification, but good for reference):

Slow Twitch (Type I) Muscle Fibers:

Slow twitch fibers rely primarily on aerobic metabolism (oxidative phosphorylation) to produce energy, making them efficient for activities like prolonged walking, jogging, and maintaining posture.

Fast Twitch (Type II) Muscle Fibers:Type IIa:

These fibers have characteristics between slow and fast twitch, offering a balance of endurance and power.

Type IIb (or IIx):

These are the fastest contracting fibers but also fatigue the quickest.
These fibers contract quickly and forcefully but fatigue faster compared to slow twitch fibers.

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These are the fastest contracting fibers but also fatigue the quickest.
Characteristics: Fast twitch fibers contract quickly and forcefully but fatigue faster compared to slow twitch fibers.
Function: Fast twitch fibers primarily use anaerobic metabolism (glycolysis) to generate energy, making them well-suited for explosive movements like sprinting, jumping, and lifting heavy weights.
Color and Appearance: They are pale or white in color due to lower myoglobin content and fewer blood vessels.

Age and Metabolism

Your Muscle Fiber Type Matters

Slow Twitch (Type I) Muscle Fibers:

Fast Twitch (Type II) Muscle Fibers:Type IIa:

Type IIb (or IIx):

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