One Bad Night of Sleep Can Make You 25% More Insulin Resistant — Here's What Actually Helps

Of everything covered in the latest Fuel with Erin conversation with hormone health coach Stephanie Crassweller, one stat stands out: a single poor night of sleep can make you up to 25% more insulin resistant the next day. Not a week of bad sleep. One night.

If you've ever eaten "the same" one day as the next and gotten wildly different results on the scale or in how you feel, sleep is very likely part of the answer — and it might matter more than the workout you're about to skip it for.

Why Sleep Outranks Almost Everything Else

Here's the chain reaction Stephanie described: when insulin stays elevated because of poor sleep, your body stays locked in a fat-storage state. At the same time, poor sleep lowers leptin — the hormone that signals fullness and tells your body it's safe to burn fat — while raising Ghrelin, your hunger hormone. So after a bad night, you're hungrier, less satisfied by food, and less able to burn fat, all while your inflammation and cortisol are climbing too.

This is why Stephanie's approach with clients who are struggling with sleep is counterintuitive: she pulls them out of early morning workouts entirely, at least temporarily. Training in a sleep-deprived, hyperinflamed, blood-sugar-dysregulated state does more harm than the workout does good. The fix isn't to push through — it's to protect sleep first, then reintroduce morning training once the body has actually recovered.

Regulation, Not Relaxation

The second half of this conversation centered on nervous system regulation — and Stephanie made a distinction worth sitting with: the goal isn't relaxation, it's removing stimulation. Those are not the same thing. A massage, a podcast, or scrolling your phone can all feel relaxing in the moment while your nervous system is still absorbing constant input.

Stephanie ran her own experiment to test this: she went three days without social media and tracked her stress levels on an Aura ring. The result was roughly two fewer hours per day spent in a measurable stress state — from cutting out one app. Her point wasn't that social media is evil; it was that we consistently underestimate how much low-grade stimulation is running in the background of an ordinary day, and how much that stimulation keeps the body in fight-or-flight even when nothing is objectively wrong.

Small, Underrated Tools That Actually Move the Needle

None of what Stephanie recommends involves an expensive protocol. A few of the tools she uses herself:

Eight slow, deep breaths before a transition. Before walking into the house to greet kids, before leaving the office, before any moment that tends to spike stress — a couple of minutes of slow breathing measurably lowers heart rate and breathing rate, training the body to recognize it's safe.

Time in genuine silence. Not a walk with headphones in, not a drive with music on — actual quiet. Reducing background stimulation, even briefly, gives the nervous system a chance to downshift out of constant alert mode.

A brain dump. When everything feels urgent, Stephanie's practice is to write down everything competing for attention and ask which of it is actually a priority today. Chronic stress convinces the brain that everything is an emergency; getting it out of your head and onto paper interrupts that pattern.

Vagus nerve tools. Humming, singing, and something as simple as an ice pack on the chest or the back of the neck can all help shift the body out of a stress response — no cold plunge required.

Boundaries around your time. Stephanie was candid that an open calendar doesn't mean she's available for everything on it. Paying attention to which people and environments leave you feeling drained versus energized is, in her words, information worth acting on — even when it means having harder conversations, especially with family.

Your Inputs Matter More Than Your Effort

One of the more useful reframes from this conversation is thinking in terms of inputs rather than actions. It's easy to focus entirely on what you're doing — the workouts, the meals, the supplements — while overlooking everything you're taking in throughout the day: the music, the conversations, the content you scroll past, the people you spend your time with. Stephanie's point is that all of it registers as a signal to your nervous system, whether or not you're consciously aware of it.

That reframe also applies to how your body responds to any intervention you're trying, from a new training program to HRT to a supplement stack. If the underlying signal your body is receiving day to day is still chronic stress, poor sleep, and constant stimulation, that signal tends to override whatever you're layering on top of it. Changing the inputs isn't a replacement for the other work — it's what makes the other work actually land.

The Bigger Point

None of these tools are complicated, and that's the point. The instinct in this stage of life is often to look for a bigger intervention — a stricter diet, a more intense workout split, a new supplement. But sleep and nervous system regulation are foundational in a way that no training plan or macro split can substitute for. Get those two things working, and the other pieces — energy, fat loss, mood — have a far better chance of actually responding.

Catch the full conversation with Stephanie Crassweller of Vitality OET on the latest episode of Fuel with Erin, including the full breakdown of why exercise recovery and workout frequency need to change too.