[00:31 – Intro]
Hi, I’m Lauri. Thanks so much for joining me today on the Your Genes by Design podcast. This is the fourth episode in the Glucose and Insulin by Design series.

In the last episode, we talked about oxygenation, which is how efficiently your body uses oxygen inside your cells to make energy.

Today we’re going to go one layer deeper into that same system and look at how your body decides what kind of fuel to burn—whether it’s going to burn glucose or fat—and why that flexibility becomes more important after the age of 45.

[01:02 – Defining Metabolic Flexibility]

You’ve probably heard that your body uses both sugar and fat for energy, but it’s not a simple on–off switch. It’s more like a dimmer that constantly adjusts.

When glucose from food is available, your body uses it first. When glucose runs low, your cells shift toward burning fat for energy.

The ability to move smoothly between these two types of fuel is called metabolic flexibility, and it plays a big role in insulin sensitivity, energy stability, and long-term metabolic health.

The smoother your body can make that transition, the steadier your energy feels, and the more balanced your glucose levels stay.

When that flexibility starts to fade, energy swings and glucose spikes become more common—even when what you’re eating hasn’t changed.

[02:22 – Why Flexibility Shifts After 45]

This is the reason why it matters after 45.

As estrogen and thyroid activity shift in midlife, the signals that regulate energy use shift too. Your muscles may not take up glucose as quickly, and your mitochondria—the parts of your cells that turn nutrients into energy—may not switch fuels as efficiently.

That’s why some women notice they can keep eating the same things, but now they feel more sluggish, they feel hungrier sooner, or they feel less stable between meals.

It’s not about willpower. It’s physiology adapting to a new balance of hormones, oxygen use, and energy demand.

The good news is that flexibility can be retrained, and your genes can help you understand how your system works best.

[03:06 – Key Genes Shaping Fuel Use]

Let’s look at this from a genetic perspective. There are several genes that influence how efficiently your body handles this fuel switch. Let’s look at a few of them.

Two were mentioned in previous episodes, but we’ll look at them from a different angle.

The first one is PPARGC1A, which supports mitochondrial creation and efficiency—or how well your cells generate energy from both glucose and fat.

If activity here is lower, you might find it harder to switch from burning sugar to fat, especially after long periods of sitting or stress.

The second one is FADS1 and FADS2, which help convert plant-based omega-3s into the active forms of EPA and DHA. Those long-chain omega-3s directly support insulin sensitivity, mitochondrial membranes, and the enzymes that control fat burning.

If you have lower FADS variants, your body might benefit from direct marine sources like salmon, sardines, or algae oil, because those nutrients support how smoothly glucose and fat are used inside your cells.

The third gene is ADIPOQ, which helps regulate adiponectin—a hormone that improves how sensitive your cells are to insulin and how effectively they use fat for energy.

When adiponectin is low, the switch between fuels can feel sticky and glucose tends to linger in the blood longer than it should.

These small differences can explain why some people thrive on higher carb days while others feel better with more healthy fats. It’s not about diet rules; it’s about how your metabolism handles fuel.

[04:43 – Everyday Signs of Flexibility]

Some everyday patterns you might notice: you can often feel this flexibility—or lack of it—in everyday life.

If you wake up hungry every morning or feel shaky between meals, your body may still be relying heavily on glucose.

If you can go a few hours without thinking about food and still feel alert, your fat-burning system is probably working well.

Neither state is good or bad. The goal is balance—where your body can shift fuels as needed without big drops or spikes.

[05:38 – Precision Mindset and Closing]

So here’s the precision piece.

Your genes don’t decide how your metabolism works, but they describe how it prefers to work.

Variants in PPARGC1A, FADS1, FADS2, and ADIPOQ shape how easily your body moves between glucose and fat.

When you know these details, you can stop guessing which habits help you most and start aligning with what your body is already designed to do.

As we close, here are a few things to think about.

We often think of energy as something to gain, but it’s really something to unblock. Your body already knows how to balance glucose and fat—it just needs clearer signals. Less rush between meals, more pause before reacting.

When you create space, your body does what it’s designed to do: to shift, adapt, and steady itself.

If this episode helps you understand how your body decides what fuel to burn, follow Your Genes by Design for more short, science-based insights made practical for life after 45.

And if you found it helpful, please share it with other women who might benefit from it.

Also, just wanted to let you know that I released a free resource for this series—The Oxygen Connection—which I’ll link to in the show notes.

That’s going to wrap things up for this episode. Thanks again for joining me, and have a great day.