Hello, hello, and welcome to today's podcast. Today we're going to be talking about metabolism in midlife. This has been coming up a lot with our patients recently, so we figured it was a great time to talk about it. Maybe people don't understand what metabolism really means, but what we're really going to focus on is insulin resistance — which is also something people may not fully understand. We hope to shed a little light on it, or at least give you food for thought and something to take to your next provider meeting.
Insulin Resistance Is Pre-Pre-Diabetes
One thing we've been saying is that insulin resistance is the "pre-pre-diabetes." The biggest crisis in our health care community right now is the onset of type 2 diabetes. There are a lot of theories about what's driving it — it's incredible that we spend so much money on health care yet have a decreasing life expectancy and increasing chronic disease. We won't go through all the causes, but we'll focus on the insulin resistance part. It's a cellular-level topic, so we'll try to keep it out of the weeds and on a superficial level so we can all have a conversation about it.
What We See in Patients' Labs
What we're seeing in our patients is a fasting glucose that's pretty normal by the standard guidelines, and even a pretty normal hemoglobin A1C — like 5.2 or 5.3, when pre-diabetes doesn't start until 5.7. So when you go to your regular doctor and they order a glucose and A1C, it looks like you're good. But we also draw the fasting insulin, and what we're seeing is that even with normal glucose and A1C, there's insulin resistance going on.
We use the HOMA-IR score, a calculation from your fasting glucose and fasting insulin — you want it close to one, which is optimal. We're finding people with HOMA-IR in the threes and fours who have no idea they're insulin resistant, and they've got metabolic syndrome. Metabolic syndrome is people with abdominal adiposity (increased waist), high blood pressure, elevated blood sugars, elevated triglycerides, and low HDL — creating this metabolic mess.
These patients didn't really have high glucose, but they did have high triglycerides, which is another indication. So when you go to the doctor and they draw triglycerides as part of a lipid panel, if your fasting glucose and A1C are normal but your triglycerides are elevated, that's an indicator to look deeper — there are enzyme issues occurring in the liver that create that problem.
The Lock-and-Key Analogy
Let me give you an analogy — it's how we remember things. With insulin resistance, insulin is like the key, and the cells are where the lock is. When the cells have a rusty lock, the key doesn't work well. You can have a lot of keys and keep trying, but it doesn't unlock the cell to allow the energy — glucose — to get in and produce its effect. So we want to make the keys very effective and decrease the rustiness of the lock on the cells.
Symptoms of Insulin Resistance
Some symptoms include belly fat, fatigue after meals, sugar cravings, skin tags, and irregular periods for women. There's also a condition called acanthosis nigricans — a dermatology condition where you get a dark, patchy appearance to the skin, especially around the neck and armpits. That's usually well advanced, going on for years. This may sound similar to PCOS, which is definitely connected — insulin resistance is one of the key drivers of PCOS, and until you correct the insulin resistance, you can't correct the symptoms.
The Primary Lab Markers
The key marker that's very rarely drawn is fasting insulin. Optimally you want it between two and six; insulin resistance is indicated when you're over 10 — but the normal range goes all the way up to 25. It's hard to believe you can call someone "normal" with an insulin of 25, because those folks are very insulin resistant. I'd like to see it under five for most people. It's a $10 lab from a self-pay standpoint — pretty cheap information.
HOMA-IR is the other one, a calculation you can't just draw — you need the components to put into the equation, which you can do online. Over two is likely indicative of insulin resistance. Fasting glucose optimally should be below 85, though normal on the labs goes up to 99 or 100. One thing about fasting glucose: a lot of things can spike it — even if you're fasting, a stressful situation or fear of needles can make it show up higher. That's another reason we look at all these markers together, because it gives us the snapshot. Some of these change within minutes, some within days, so fasting is the best way.
Hemoglobin A1C is a picture of what your blood sugar has done over the past three months. It can catch things like a good fasting glucose in someone who eats a lot of sweets and spikes frequently. The CDC says diabetes starts at 6.5 and pre-diabetes is 5.7 to 6.4, but we like to see it close to five — not easy, you have to watch sugars, breads, and alcohol.
The triglyceride-to-HDL ratio optimally needs to be one-to-one; elevated triglycerides and lower HDL throw it off and can indicate early insulin resistance — and that's not just a reason to take a statin, there are other problems going on. Uric acid is another marker — a way to look at sugar more on the fructose side; optimally less than 5.5, varying a bit by sex. Excess uric acid can lead to gout, but it's a diet-related, controllable problem — not the fructose in fruit (which has fiber and enters slowly), but the high-fructose corn syrup in sodas. Uric acid is also an inflammatory marker tied to atherosclerotic heart disease and inflammation affecting the brain, heart, and liver. And the liver enzymes ALT and AST — when ALT is higher than AST, you start looking at fatty liver disease, closely related to insulin resistance. If your bloodstream always has sugar floating around that isn't used efficiently, the liver stores it as fat.
Pre-Diabetes and Diabetes Numbers
Insulin resistance is pre-pre-diabetes; then pre-diabetes fasting glucose is 100 to 125, and 126 or higher is technically diabetic. A1C above 6.5 is diabetic. There's also the two-hour glucose tolerance test where you drink about the sugar equivalent of two cans of Coke — a two-hour glucose under 140 is optimal, 140 to 199 is pre-diabetic, and over 200 is diabetic. With impaired glucose metabolism, our body is just having trouble managing blood sugar because we're pounding it too much.
Another analogy: diabetes is like a sugar traffic jam. Your bloodstream is the highway, glucose is the delivery trucks bringing fuel, and insulin is the traffic cop directing those trucks off the highway into the fuel storage stations — your muscles, brain, and organs. When the traffic cop isn't working properly, the fuel stations don't respond, everything backs up, and that's where damage to the organs begins.
Metabolic Flexibility
Metabolic flexibility is getting your body good at burning sugar and then transitioning to burning fat. Think of it like a hybrid car: burning gas is burning glucose, and running on electric is burning fat. Glucose is for quick-burn efficiency and fast movements; fat is for long-lasting endurance.
After a meal we want to burn glucose to move it through our system, but overnight we want to tap into fat stores as we rest and recover. On a long walk or marathon — this is where VO2 max testing comes in — you burn both. Zone 2, conversation-pace activity burns more fat, but when you're huffing up a hill, your body grabs glucose because it needs energy faster.
How Inflexibility Shows Up
In real life, inefficiency shows up as an energy roller coaster — feeling good after eating, then crashing an hour or two later, or an afternoon slump where you reach for snacks, coffee, or sugar to feel awake again. When your body isn't metabolically flexible, it panics when carbs aren't readily available, triggering cravings for sugar or salt — things quick to process. People get "hangry." It's also why timed-eating or fasting can be hard to stick to.
Weight gain, especially around the middle, is another sign — insulin resistance traps fat in storage mode. If we increase carbs and calories without using them, insulin takes it to storage and makes fat to keep for later. Higher insulin levels cause hypertrophy of fatty tissue, making it harder to get rid of. Metabolic inflexibility can also affect sleep — blood sugar crashes dipping too low cause restless sleep or early waking, and without stable energy from fat, your body can't repair properly at night. And glucose spikes and crashes cause brain fog and mood swings, because steady energy affects neurotransmitter production and mood regulation.
Increased Risk for Chronic Disease
Insulin resistance is the root cause of type 2 diabetes, heart disease, PCOS, and Alzheimer's (commonly referred to lately as type 3 diabetes). It's a driving force for chronic disease — and even some cancers tie back to it — so it has to be addressed and understood.
Why It Happens in Midlife
Why does insulin resistance happen so much in midlife? Hormonal changes, differently for each sex. For women, perimenopause brings fluctuations in estrogen and progesterone that directly impact insulin sensitivity at the cellular level, leading to fat distribution changes, fatigue, and brain fog. For men, testosterone slowly declines, decreasing the metabolic rate. Women are at a disadvantage because it happens rapidly in perimenopause, whereas for men it's a slow, decades-long, less noticeable process (the classic "beer belly").
The loss of muscle also contributes. Muscle mass declines every decade after 30, and muscle is the primary glucose disposal — the easiest, fastest way to get rid of glucose. Muscle can both absorb glucose directly and take it in from insulin, a double effect — which is why we stress exercise. And as cells age, they don't work as efficiently, so we've got to keep the mitochondria efficient, replacing the poorly functioning ones through activity and exercise.
Lifestyle accumulation matters too — habits like sitting more, eating processed foods and carbs, poor sleep, and chronic stress accumulate over time and create inflexibility, along with increased inflammation and oxidative stress that worsen insulin resistance.
Training Your Metabolism to Be Flexible
First on the list: fasting — but more specifically intermittent fasting. Some people do well with 24-hour or longer fasts, but you can get similar insulin-improving effects with intermittent fasting, which I prefer to call feeding windows. We eat in designated times, and when we're not eating, the body rests, digests, and repairs, improving insulin sensitivity. More time between the last calorie of one day and the first calorie of the next lets insulin slow down and reset. In modern life the body never goes without, so it's always expecting more food and keeping insulin high. If food is always available, we eat it — so some people keep less food in the fridge or pantry to allow more caloric restriction.
Low-glycemic meals — think about the foods themselves (protein, fat, and fiber). Carbs are not the enemy; you need them in the form of colored vegetables, leafy greens, and some fruit. The right source matters — jelly beans are different from broccoli. Also think about the way you eat: front-loading your meal with protein, fat, and fiber slows mobility, so you can probably get away with a little bread or a few chips.
Movement after a meal — even air squats. I had a patient who couldn't give up her Coke, so I said, "You can have your Coke, but give me 20 air squats every time you drink one." Take your wins when you can. Getting up and activating the muscles and mitochondria takes up glucose, slowing your spike and reducing your insulin spike, so you have less insulin resistance.
Testing and Tracking
We've covered the lab tests — fasting insulin, HOMA-IR, hemoglobin A1C, and the triglyceride-to-HDL ratio are the key markers. Also watch waist circumference — optimally under 30 for females and 35 for males. Track energy patterns: does your afternoon slump happen after lunch, and what did you eat? And listen to your cravings — sugar and starches are quick to process; people rarely crave meat or fiber, so we have to feed the body correctly.
Another way to track is a continuous glucose monitor (CGM) — you don't have to be diabetic to use one for good data. Everybody is different; something I eat might react very differently in my body than in someone else's. Most people spike on a grape, though some don't. A CGM is also great for seeing how stress and different workouts affect your blood sugar — you can tell you're less metabolically flexible after a bad night's sleep. You don't need to wear one for months; experimenting for two weeks (about one monitor's life) is enough. Dexcom recently came out with an over-the-counter product called Stelo, a good way to peek at how different foods affect you. I wore a CGM during a marathon and saw my blood sugar go up 30 points at one point — that's stress affecting blood sugar.
Putting It All Together
A 10-to-15-minute walk after a meal is a good thing. Focus on protein, fats, and fiber with each meal to slow absorption. Manage stress with deep breathing, meditation, or yoga — yoga is especially beneficial because it stimulates the muscles to reduce glucose while relaxing you.
Strength training — muscle is our best organ for fighting blood sugar issues, and it declines as we age, so start high. You can build muscle at any age; it gets harder the older you get, but you can do it, so start as early as you can. Zone 2 cardio (conversation-pace) burns fat and helps insulin resistance.
Track and learn — pay attention to how you feel after a certain meal. As I started listening to my body, I gave up some favorite meals; sushi and Mexican I now eat sparingly, because they didn't feel good — though before I had the data, I'd eat them anyway. Those tortilla chips get everybody.
Prioritize sleep — consistent bedtime and wake time improve sleep quality. Cut down screens and stimulation at bedtime; keep it bland with the lights low, sleep in a dark place, and don't fall asleep with the TV on. And whole-food nutrition is key for cellular health — cut out processed foods and shop the perimeter of the grocery store, the produce and meat aisles. The good stuff is on the outside.
We hope we've given you information to make decisions about your own health. Just understand that insulin resistance is a major contributor to chronic disease, period, and chronic disease is on the rise — it's a crisis. Yes, there are issues with food availability and how it's made, but there are things you can do to help yourself. Reach out if you have any questions, and otherwise we'll see you next time. Have a healthy day.