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By Tony Mathews, MD, MPH, Medical Strategist, Sequoia Medical 360 in Bronxville 

April 29, 2026: If you are joining us this week, below are links to the first four 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 3: Health and Wellness: Precision vs. Habit. The Nutrition Debate No One Wins. Two Things You Can Do This Week

Week 4: The Calorie Question - Awareness Matters More Than Precision. Two Things You Can Do This Week

This week's article below focuses on The Metabolic Playbook

Dr. Tony Mathews

Week 5: The Metabolic Playbook

The Insulin Question The hormone that decides what your food becomes.

If there is one hormone that shapes how your body handles food, stores energy, and ages over time, it is insulin. Most people think of it only in the context of diabetes, but insulin is working every minute of every day, in every person, healthy or not. Understanding what it does is one of the most useful things you can learn about your own metabolism.

When you eat, your blood sugar rises. Your pancreas releases insulin to bring it back down. Insulin acts like a key, opening the doors of your cells so that sugar can move out of the bloodstream and into the muscles, the liver, and fat tissue, where it gets used for energy or stored for later. This happens after every meal, in the background, without you ever noticing.

The problem is that the system can get worn down. When the cells stop responding to insulin the way they used to, the pancreas has to work harder, releasing more and more of it just to keep blood sugar in a normal range. This is insulin resistance, and it is one of the most common and least diagnosed conditions in modern medicine. It can develop quietly for ten to fifteen years before blood sugar ever shows up as abnormal on a routine lab.

Why This Matters for Weight

Insulin is not just a blood sugar hormone. It is also a storage hormone. When insulin is elevated, your body favors storage. When insulin is low, your body more easily draws from its existing fuel stores, including fat.

This doesn't mean that insulin overrides calories. The research is clear that sustained energy balance is still the primary driver of weight change. But the hormonal environment surrounding your food shapes hunger, satiety, energy, and where weight tends to be stored. For people with normal insulin sensitivity, this background influence is modest. For people with significant insulin resistance, it can be the difference between weight loss feeling manageable and feeling impossible.

This is also why insulin resistance makes weight loss frustrating for so many people. Even with disciplined eating and exercise, an insulin-resistant body fights harder to give up its stored energy. People in this state often describe doing everything right and getting nowhere. They are not imagining it. Their biology is making the same effort cost more.

What Drives Insulin Resistance

A few things consistently push insulin resistance in the wrong direction. Excess body fat, especially visceral fat around the organs, is a major driver. So is a diet high in refined carbohydrates and added sugars, which forces frequent and prolonged insulin spikes. Poor sleep raises insulin resistance measurably within just a few nights. Chronic stress contributes through cortisol, which we will discuss next week. And inactivity matters more than most people realize, because muscle is one of the body's main sites for clearing sugar from the blood.

There is also a genetic component. Some people are simply more prone to insulin resistance regardless of what they eat or weigh. This is especially common in people of South Asian, East Asian, Hispanic, and African ancestry, where insulin resistance can develop at lower body weights than what standard guidelines would flag as concerning.

What You Can Watch

Standard bloodwork rarely tells the full story. A fasting glucose can look completely normal while insulin is already elevated and working overtime in the background. The two markers that tell a more complete picture are fasting insulin and hemoglobin A1c, with fasting insulin being the earliest warning sign. A calculation called HOMA-IR, derived from fasting glucose and fasting insulin, gives a useful estimate of insulin sensitivity. These are widely available tests and can easily be added to a standard panel.

Two Things You Can Do This Week

1. Anchor your meals with protein and the right kind of fiber. Both blunt the insulin response to a meal, but not all fiber works the same way. Soluble, viscous fibers — found in oats, beans, lentils, chia seeds, psyllium, and many vegetables — are the most effective at slowing carbohydrate absorption and reducing insulin spikes. Starting your meal with protein or vegetables before getting to the starch leads to a smaller blood sugar rise and a smaller insulin response. This simple shift in meal sequencing has measurable effects in clinical studies.

2. Move after meals. A ten- to fifteen-minute walk after eating, even at a casual pace, reduces post-meal blood sugar significantly. Muscle pulls sugar out of the bloodstream without needing as much insulin to do it. This is one of the most underused tools in metabolic health, and it costs nothing.

The Takeaway

Insulin is the quiet hand behind weight, energy, and metabolic health. When it works well, food becomes fuel. When it doesn't, food becomes storage more easily, and weight loss becomes harder than the calorie math would suggest. Most people never get a clear picture of where they stand because the standard tests don't ask the right questions.

Eating well and moving more will improve insulin sensitivity for almost anyone. But if you have been doing the right things and your weight or energy still isn't responding, looking at insulin directly is one of the most useful next steps. It can help explain why progress has been slower than expected.

These are tests you can ask for, and changes you can start today. But if you want to understand what the numbers mean for you specifically, working with a physician who looks beyond standard panels can make the difference between guessing and knowing.

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.