Why You’re Always Tired

Key insight: Real energy comes from how sleep, stress, nutrition, and movement work together.To avoid crashes, small, consistent tweaks in all four matter more than big efforts in one.

We surveyed 1,897 Welltory users to uncover how eating patterns and daily habits shapeenergy, and what gets in the way of feeling consistently good.

What the science says: Blood sugar spikes after meals can be one of several reasons behindfatigue and energy crashes, but they’re not the whole story. It’s a myth that when you eat makesa difference, since research shows timing alone doesn’t matter. What matters most is how muchyou eat, which plays the biggest role in weight control, while what you eat can sometimesinfluence how steady your energy levels feel.

Energy isn’t only about how long you sleep or how much stress you’re under — both mattera lot, but even 7–8 hours of sleep may not be enough if stress is high or your body is runningon too few calories.

A big piece of the puzzle is how your metabolism works: not just how your body handles food, but how hungry you feel, how steady your blood sugar stays, and how well you recover. Strong hunger often comes with poor sleep or emotional stress, which can lead to weight gain and setoff the whole chain toward insulin resistance. On the flip side, stress can sometimes suppress hunger, pushing your body to burn through liver glycogen under the influence of stresshormones.

Your body works hard to keep blood sugar steady. If it drops too low, different systems kick in to raise it back up. If it gets too high, other systems step in to bring it down. The goal is always the same: a state called glucose homeostasis. This simply means your body is keeping blood sugar within a healthy, steady range. It's the balance point where glucose isn't too high or too low, so your cells get the fuel they need.

What the science says: Feeling sleepy after eating is completely normal: it’s your body doing exactly what it’s supposed to. After a meal, amino acids circulate in your blood. Both BCAAs and tryptophan rely on the same transporter to cross into the brain, so they compete with each other. When insulin is working well, it helps move more BCAAs into your muscles, which reduces the competition at that transporter. As a result, more tryptophan enters the brain, where it’s converted into serotonin and, later in the evening, melatonin. That’s why post-meal sleepiness can actually be a sign of good insulin sensitivity, not poor glucose control.

Another reason you feel less alert is cortisol, your main “get up and go” hormone, naturally drops after eating. During stress or fasting, cortisol keeps you energized by breaking down fat and releasing glucose. But once you’ve eaten, those processes stop: instead of mobilizing fuel, your body focuses on storing glucose in muscles, liver, and fat cells. So, after you eat, insulin, leptin, and the parasympathetic nervous system all work together to dial down cortisol, helping your body shift into rest-and-digest mode.

A large lifestyle study published in the International Journal of Behavioral Nutrition and Physical Activity found that higher BMI and lower activity levels predicted the development of insulin resistance, while people with lower BMI were much less likely to develop it.

A recent genetic study published in Nature confirmed this: genetic variants that raise insulin and glucose were actually linked to lower body fat and BMI, not higher. In other words, having a predisposition to insulin resistance does not make you gain weight.

The good news is anyone can check for insulin resistance using standard blood tests (fasting glucose + insulin, or a panel such as HOMA-IR). In the US, a basic fasting insulin test costs about $30–60, while more detailed panels run $80–250. Even without insurance, you can usually check for insulin resistance for under $100.

What the science says: Caffeine gives a temporary energy boost but can also act like other addictive substances. Studies show that caffeine dependence can cause distress, disrupt daily functioning, and even require treatment in some cases. The study published on PubMed looking at caffeine after a night of fragmented sleep found it worsened glucose control the next morning—but importantly, fragmented sleep alone (in that study) didn’t show the same effect.

This suggests the combo of poor sleep and caffeine may be what drives the problem, though more research is needed.

What the science says: Stress normally triggers the release of glucose into the bloodstream, suppressing appetite in the short term. But for many people, stress leads to cravings for high-calorie comfort foods. Research shows that frequent stress eating is linked to worse glucose control, prediabetes, and higher diabetes risk.

What the science says: Poor sleep doesn’t just leave you feeling tired—it also disrupts how your body manages glucose.

What the science says: Hair growth naturally follows a cycle: most strands (around 85%) are actively growing, while the rest are resting or preparing to shed. When inflammation rises in the body—often because of excess body fat—special proteins called inflammatory cytokines circulate in the blood. Since hair follicles are nourished by the same blood supply as the rest of the body, they “hear” this inflammatory signal. The message is essentially: “We’re in survival mode, conserve energy, stop growing hair.” As a result, follicles cut short the growth phase, shift into rest, and hair sheds earlier than it should.

Nutrition adds another layer. A lack of dietary protein doesn’t usually cause shedding, but it does weaken hair structure, leading to brittleness and slower growth. Carbohydrate-heavy diets can make this worse by crowding out protein intake.

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Simple, low-willpower actions that deliver the biggest payoff.

People aren’t just tired because of stress or sleep debt—for many, their metabolism is out of sync. At Welltory, we believe true health means understanding not just stress and recovery, but also how metabolism shapes your training loads, sleep quality, and nutrition choices.

To give you even more energy insights, we’ve partnered with Nutrisense—an app that helps people connect the dots between meals, glucose responses, and daily habits, turning insights into sustainable systems that actually work in real life.

When you can see both your nervous system recovery (through HRV) and your metabolic patterns (through glucose), you stop guessing and start leading. This is what we call Metabolic Intelligence—the foundation for sustained energy, better recovery, and improved wellbeing.

Almost 2,000 people told us the same thing: “I’m tired, even when I shouldn’t be.” Behind the grogginess, cravings, and crashes is your metabolism asking for balance. When you connect stress, sleep, and food, you get clarity. And with clarity comes power—the power to reclaim your energy and finally feel in sync with your body.