Health & Wellness: What Chronic Stress Actually Does
By Tony Mathews, MD, MPH, Sequoia Medical 360 in Bronxville
June 17, 2026: If you are joining us this week, below are links to the first five articles in this series.
Week 1: The Number on the Scale Is Lying to You - Two Things You Can Do This Week
Week 2: Your True North: How to Build a Real Health Baseline - Two Things You Can Do This Week
Week 4: The Calorie Question - Awareness Matters More Than Precision. Two Things You Can Do This Week
Week 5: The Metabolic Playbook
This week's article below focuses on why stress and poor sleep may be the metabolic levers you've been ignoring.
Dr. Tony Matthews
June 17, 2026: You're eating well. You're exercising. You're doing the things you're supposed to do. And the weight still won't budge, or the energy still isn't there. Before you blame your discipline, there's a question worth asking: how are you sleeping, and how stressed are you?
I bring this up because it's the part of the picture people most often leave out. Someone will hand me a detailed food log and a workout schedule, and when I ask about sleep, she waves it off. Five or six hours, she says, like it's a badge of honor. But that detail often explains more about why she's stuck than anything on the food log.
The hormone behind this is cortisol. It's your body's main stress hormone, and it isn't the villain it's often made out to be. You need cortisol. It wakes you up in the morning, helps you respond to challenges, and keeps you alert when it matters. The problem isn't cortisol itself. The problem is cortisol that never gets to come down.
What Chronic Stress Actually Does
Cortisol is designed to spike and then recede. You face a stressor, your body mobilizes, the threat passes, and the system resets. That's healthy. What's not healthy is the modern pattern, where the stress never really ends. Work, finances, family, the phone that never stops. The body stays in a low-grade state of alert that it was never built to sustain.
When cortisol stays elevated, a few things happen that matter for your metabolism. It raises blood sugar, because its job is to make energy available for a threat that, in this case, never arrives. That extra sugar triggers insulin, the hormone we talked about last week, and over time that contributes to insulin resistance. Chronically high cortisol also tends to drive fat storage specifically around the abdomen, which is the most metabolically harmful place to carry it. And it stokes cravings, particularly for sugar and refined carbohydrates, because your body is looking for quick fuel.
So the person doing everything right but staying stressed and underslept is fighting their own physiology. The effort is real. It's just being undercut by a hormone they never thought to consider.
The Sleep Connection
Sleep is where this becomes most actionable, because poor sleep and high cortisol feed each other. Stress makes it harder to sleep, and poor sleep raises cortisol the next day. It's a loop, and it's one of the most common ones I see.
The metabolic cost of poor sleep is not subtle. Even a few nights of short sleep measurably increases insulin resistance in healthy people. It disrupts the hormones that govern hunger, raising ghrelin, which makes you hungry, and lowering leptin, which tells you you're full. This is why a bad night so often leads to a day of grazing and craving. You're not weak. Your hunger signaling has genuinely been altered.
For most people, sleep is the single highest-leverage change available, and it's the one they're most likely to sacrifice first.
Two Things You Can Do This Week
1. Protect a consistent sleep window. Pick a bedtime and a wake time and hold them, even on weekends. Consistency matters as much as duration. Going to bed and waking up at roughly the same time trains your cortisol rhythm to do what it's supposed to: high in the morning, low at night. If you can manage seven to eight hours in that window, you'll likely feel the difference within a week.
2. Build one real recovery point into your day. Not your phone, not the news, not a glass of wine. Something that genuinely lowers your stress response: a ten-minute walk outside, a few minutes of slow breathing, time with people you actually enjoy, a stretch of quiet before bed. The goal is to give your nervous system a real signal that the threat has passed, so cortisol can come down the way it's supposed to.
The Takeaway
You can do everything right with food and exercise and still stall out if stress and sleep are working against you. Cortisol is a quiet lever, and most people never think to check it. The good news is that it responds. Better sleep and genuine recovery improve insulin sensitivity, reduce cravings, and make every other effort you're making work better.
These are changes you can start tonight. But if you've cleaned up your sleep and managed your stress and things still aren't moving, that's worth a closer look. Chronic stress, sleep disorders, and hormonal patterns sometimes need more than willpower to untangle, and knowing when you've crossed from a habit problem into something physiological is part of what a physician is there to help you see.
Up next: The Protein Question. What the research actually says, and what the gym influencers get wrong.
This article is for educational purposes only and does not substitute for individualized medical advice. Dr. Tony Mathews is a longevity medicine physician and the founder of Sequoia Medical 360 based in Bronxville, NY.
