Insulin Resistance, CGM’s, & Blood Sugar Spikes: Breaking Down the Confusion
BLACK IRON RADIO EP. 390: Insulin Resistance, CGM’s, & Blood Sugar Spikes: Breaking Down the Confusion
Somewhere along the way, the internet decided your blood sugar going up after you eat is a problem. It isn't! That's your body doing exactly what it's built to do.
Amanda, Joyce, and Morgan break down the confusion around insulin resistance, continuous glucose monitors, and blood sugar spikes. They get into what's actually normal versus what's genuinely dysfunctional, why two healthy people can eat the same meal and get completely different glucose responses, and why chasing a perfectly flat line is both pointless and sometimes a red flag in itself. They talk through the fear-based content that gets rewarded online, why fruit is not the enemy, why insulin is not the enemy, and what actually matters for metabolic health.
Plus why a flat glucose curve can be hiding a serious problem, why most people wearing a CGM for fun are getting nothing useful out of it, and the genuinely boring stuff that moves the needle: muscle, movement, sleep, and a walk after you eat.
Somewhere on TikTok right now, someone is telling you your oatmeal is trying to kill you. So you look at your breakfast, wonder if the banana on top is "spiking" you, and start pricing out a continuous glucose monitor to make sure you survive a bowl of oats. Meanwhile, nothing is wrong with you. Your blood sugar went up after you ate because that is what blood sugar does.
In this episode of Black Iron Radio, Amanda, Joyce, and Morgan sort out the difference between normal short-term physiology and actual long-term dysfunction. They cover what insulin does, what insulin resistance is and isn't, who a CGM is actually for, and what moves the needle on metabolic health without a gadget stuck to your arm.
What Insulin Actually Does When You Eat
Insulin is a peptide hormone made by your pancreas, and it's the main anabolic hormone in your body. Its job is coordinating nutrient metabolism: moving glucose out of your bloodstream and into your muscle, liver, and fat cells to be used or stored.
The sequence is simple. You eat carbohydrates or protein (yes, protein triggers insulin too). Your digestive system breaks the food down and sends it into circulation, so your blood glucose rises. Your pancreas detects that and releases insulin, which drives glucose into your tissues, signals glycogen synthesis, and tells your liver to stop putting its own sugar into your blood since plenty is already coming in from food.
How fast and how high glucose rises depends on a long list of things: fiber, protein, and fat in the meal, whether it's liquid or solid, how it was cooked, and how quickly your stomach empties. Then there's everything about you that day. Your sleep, your stress, your training over the last few days, your muscle glycogen status, where you are in your menstrual cycle, the time of day, and whether you're sick all change the response.
That's why two healthy people can eat the exact same meal and get very different glucose curves. It's also why you can eat the same meal on two different Mondays at 7:00 AM and get two different curves. A single reading in isolation is close to meaningless.
Your Blood Sugar Is Supposed to Move
If nothing happened to your blood sugar after you ate, that would be the alarming result. As Morgan put it, chasing a flat glucose curve is like taking a screenshot of a comatose patient's chart and deciding that's the goal.
Your body is a dynamic system. Your weight changes hour to hour. Your blood pressure changes. Your heart rate isn't supposed to be 65 beats per minute on the couch and also 65 in the middle of 50 burpees for time. Nobody panics when the thermostat kicks the AC on and then off again, because that's a self-regulating system doing its job. Glucose going up, insulin responding, and glucose coming back down to a healthy range is the same thing.
It's the detox craze all over again. Ask a nutritionist about a detox plan and the answer is "do you have a liver?" We've now pathologized the fact that your body works.
So why is this everywhere? Because fear gets paid. Content that makes you scared of your food gets more views, more comments, and more sales, and a lot of the people posting their glucose graphs aren't diabetic or prediabetic in the first place. The question that actually matters isn't "how high did it go," it's whether the response is predictable and resolves itself. If your glucose is still sky high three or four hours after a meal, that's worth looking into. If it rose and came back down, that's a system working.
Insulin Resistance Is Your Cells Ignoring the Signal
Insulin resistance is real, and it is dysfunctional physiology. It's also not a diagnosis of diabetes, and it's not something you get to self-diagnose off a reel.
Here's the mechanism. Insulin shows up and says there's glucose and amino acids waiting in the bloodstream, come pick them up. In insulin resistance, the cells ignore it. The reason they ignore it is that they're already full. The primary driver of true insulin resistance is excess energy stored in your tissues, and refusing more is a protective mechanism for the cell.
It happens like this. When you eat more energy than you burn over a long period of time, it gets stored in fat cells. Fat cells only have so much room. Once they hit capacity, fat starts spilling into the bloodstream and accumulating in muscle and in the liver. In the liver, that's fatty liver, which leads to excess glucose production, higher blood sugar, and more LDL cholesterol. Since the liver is one of the most important organs for metabolic function, the effects run downstream from there.
Two details matter here. First, this builds slowly. People often become insulin resistant 5, 10, or 15-plus years before a prediabetes or type 2 diabetes diagnosis. It's a sliding scale, not a switch. Second, your pancreas compensates by pumping out more and more insulin, which means blood sugar can look perfectly normal while things are drifting in the wrong direction. That chronically high insulin can also affect other hormone systems. In women it can push testosterone up, which is one of the hallmarks of PCOS.
The good news is that insulin resistance is very responsive. Diet and lifestyle changes can reverse it, and quickly. You use up the stored energy by moving more, eating in a calorie deficit, or both.
Insulin Resistance Does Not Make You Fat Loss Resistant
This is the internet claim Amanda finds most frustrating, because fat loss is literally how you fix insulin resistance. It works the same way it does for anyone else. Energy balance drives fat loss. If you're not losing weight, you're not in a calorie deficit.
Morgan's point is that the pseudoscience crowd flips cause and effect. They tell you the thing you're living with is the reason you can't change, when really the surplus came first and insulin resistance is the result. One of the main ways you become insulin resistant is being in a surplus for a long time. That's the elephant in the room.
It's also just not how human metabolism works. If we were so fragile that a blood sugar spike at breakfast broke everything, humans wouldn't have made it this far, across wildly different diets, cultures, and athletic demands. A normal insulin response to a meal is not the same thing as hyperinsulinemia, which is insulin that's elevated all the time regardless of what you just ate.
What a CGM Is Actually For
Continuous glucose monitors are incredible technology for the people who need them. If you have diabetes, use insulin, or are at meaningful risk of hypoglycemia, that data makes treatment safer, easier, and more precise. It catches lows, significant highs, overnight changes, and medication responses, and it helps you and your provider make decisions.
For a metabolically healthy person, there is no evidence that wearing one improves long-term health or prevents diabetes.
A CGM also isn't sitting in your bloodstream measuring your blood every second. It estimates glucose from interstitial fluid, the fluid surrounding your cells. That correlates well with blood glucose, but there's a lag, especially when glucose is changing fast, and it can disagree with a finger stick during those windows.
So picture someone with no context watching the numbers go 97, then 142, then back to 118, and building a whole story around it. Was it the banana? Should I never eat bananas again? The number tells you nothing about your insulin response, whether it would happen again, or whether you slept badly, were stressed, or had just trained. More data doesn't create more understanding. It creates one more thing to worry about.
Fitness trackers were the warm-up for this. Morgan has friends, a new mom and a high-performance athlete among them, who canceled their Whoop memberships because being told over and over that they were under-recovered, with nothing they could do about it, was wearing on them. Someone can be exercising daily, averaging 6,000 to 8,000 steps, sleeping well, eating enough protein and fiber, and not be in a surplus, and still be panicking over a graph. If you don't have a medical need, this information can do more harm than good.
Four Myths Worth Dropping
"Every glucose spike is doing long-term damage." Chronically elevated glucose in diabetes does damage blood vessels over time. That doesn't mean an hour-long rise after a meal is doing the same thing. It's like saying that because high blood pressure is harmful, your blood pressure going up during exercise must be hurting you.
"A flat glucose curve means you're healthy." A client once sent Amanda a completely flat chart and asked, "Isn't this so cool?" Amanda's first question was whether she'd eaten that day. If you're getting a flat line by avoiding carbs, undereating, skipping fruit, or anxiously pairing every carb with fat and protein, that's a red flag, not a win. And as Morgan pointed out, a line can be flat at 210, which is not good news either.
"Fruit spikes your blood sugar, so skip it." It's reductionist to write off a banana's potassium, vitamin C, magnesium, B6, and fiber because of one small bump two hours after you ate it. Look at the whole food, not one biomarker.
"Insulin makes you gain fat." Insulin does participate in nutrient storage, but your body stores and releases energy all day long. Fat gain is about what happens across weeks and months. Protein stimulates insulin too, so if insulin were inherently bad we'd have to start warning people off protein, which would be wild.
What Actually Tells You About Your Metabolic Health
Metabolic health is a systems-level question. It's never one snapshot, and it's definitely not what happened after one meal. Get these through your doctor, not a mail-in kit.
Fasting glucose: where it typically sits is a useful indicator. Repeated fasting readings over 200 are a problem and need to be checked out.
Hemoglobin A1C: this one accounts for time, reflecting your average blood sugar over the past two to three months. It's worth tracking as you age or if you have metabolic concerns.
Fasting insulin: it can be an indicator, but since your pancreas can compensate, it doesn't tell the whole story on its own.
Blood pressure and lipids: your average blood pressure over time, your triglycerides, and your cholesterol, and whether they sit in a healthy reference range.
Body composition and visceral fat: fat stored around your organs matters more than body fat in general. If you notice you're gaining there specifically, that's a sign of metabolic dysfunction.
Activity, sleep, and stress: whether you move throughout the day, challenge your cardiovascular system, resistance train, sleep well, and manage stress.
Family history and overall diet: genetics do matter for predisposition, and so do both the quality and quantity of what you eat.
If you get labs back and don't know what they mean, bring them to someone qualified to read them. A random influencer is not that person.
How to Improve Insulin Sensitivity Without a Gadget
There is no magic supplement here. It's the boring stuff, and the boring stuff works.
Sleep: Morgan's take is that people should be far more concerned about a bad night of sleep than a glucose spike. If you want something to be scared of, be scared of that.
Build and use your muscle: muscle is a glycogen sink. Someone active with a good amount of muscle can drink 100 grams of straight liquid carbohydrate and barely see a blood sugar increase, while someone inactive might see a massive spike and drop. It's not the food. Exercise improves insulin sensitivity immediately, and the effect lasts 24 to 48 hours or more.
Walk after you eat: ten minutes after a meal is enough. It's one of the first things Joyce recommends when a client shows up with a high A1C, and it's good for digestion and your head too. Even one meal a day counts.
Lift, don't just run: if you run five days a week, consider strength training three times and running twice. Muscle mass affects these markers directly, and it's about a lot more than how your glutes look in shorts.
Keep your energy balance in check: you don't want to live in a deficit, and you don't want to live in a surplus. One big dinner isn't the issue. Prolonged, consistent overeating is. If you carry excess body fat, a longer deficit makes sense. If you're at a healthy body fat, focus on maintenance and food quality.
Get enough protein: somewhere between 1.4 and 2.2 grams per kilogram of body weight covers most people, with very active people on the higher end.
Take fiber seriously: aim for about 15 grams per 1,000 calories, increase it gradually so your digestion doesn't revolt, and get it from a variety of sources so you're covering both soluble and insoluble. Everyone's hitting protein now. Fiber is the unsung hero, and it matters for more than blood sugar, especially with colon cancer showing up in younger people.
Eat your fruits and vegetables: antioxidants improve blood glucose control and insulin sensitivity. If a food has a deep color or a pungent smell or taste, coffee included, it's safe to assume it's rich in micronutrients. Frozen and canned vegetables are just as good, so a produce recall is not a reason to go weeks without a green.
What You Can't Control
You can also be at a healthy body weight and still have insulin resistance, since visceral fat can accumulate without a lot of overall body fat. Body size alone doesn't tell you anyone's metabolic health.
Joyce sees the limits of control with her pregnant clients. They lift, eat well, hit their protein and fiber, and some still end up with gestational diabetes and wonder what they did wrong. Nothing. It has a lot to do with the placenta, and nobody gets to choose how theirs grows.
The same nuance applies to PCOS. A diagnosis doesn't automatically mean you're insulin resistant, and insulin resistance doesn't mean you can't eat carbs. It means the conversation gets more specific about energy balance, meal composition, and which carbs you prioritize.
You don't have to be perfect to be healthy. As Amanda says, C's get degrees.
The Takeaway
Stop confusing normal physiology with pathology. Your blood sugar is not supposed to be a flat line, carbs are not the enemy, and a temporary rise after a meal is not proof that your body is broken. Insulin is not something to fear or micromanage, and a CGM is not a crystal ball for metabolic health unless you have a medical reason to wear one.
Insulin resistance is real, it builds over years of surplus, and it's reversible. The way to stay insulin sensitive is the same list it always is: manage your energy balance, eat mostly whole foods with plenty of protein, fiber, and plants, lift, move, sleep, and manage your stress. Don't try to biohack your blood sugar into a flat line. Build a body that's resilient enough to handle the ups and downs.
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If you enjoyed this conversation, check out more episodes of Black Iron Radio, where we cut through the noise and give you real, no-BS advice on feeling, performing, and looking your best. Each week we share practical nutrition, training, and wellness strategies and tips to help you succeed.
