Why Am I So Tired? What to Eat for All-Day Energy
We all know the feeling: the 3 p.m. crash. You reach for an energy drink or a candy bar to push through the afternoon slump. The promise of a quick energy fix that, an hour later, leaves you even more depleted than before.
Here's the problem: sugar delivers energy in its most fleeting form. It spikes your blood sugar, then drops you, hard. The real goal isn't a quick jolt. It's sustained energy: steady, even fuel that powers your body and brain for hours, not minutes.
The good news? A low carb lifestyle (~100 g net carbs per day) is uniquely positioned to deliver exactly that. Here's the science behind lasting energy, and how to eat (and live) for it.
Why Sugar and Caffeine Backfire
When you eat a sugary snack or sip a sweetened latte, your blood sugar spikes quickly, triggering a surge of insulin to bring it back down. That's the energy "high." But what follows is the crash: your blood sugar dips below baseline, leaving you craving the next hit of sugar just to feel normal again. It's a cycle, not a solution.
Low carb eating breaks this pattern by helping stabilize your blood sugar in the first place. When you're not riding a glucose rollercoaster all day, you're not fighting the highs and lows that are known as your "energy problem."
TIP: Eating the right carbs at the right time, paired strategically with protein and healthy fats, keeps you energized and mentally sharp without the dreaded blood sugar crash.
What's Secretly Draining Your Energy?
Before reaching for another piece of candy, it's worth asking: is something deeper sapping your fuel? Here are a few common, often-overlooked culprits:
- You're not eating enough. Chronic undereating, even in a low carb context, can leave your body without enough fuel to function optimally, leading to fatigue, brain fog and a sluggish metabolism. This may also become a factor when using GLP-1 medications.
- Iron deficiency Anemia. Low iron levels are among the most common drivers of fatigue, and women are especially vulnerable. Premenopausal and pregnant women, along with children, the elderly, and those eating a plant-based diet, are more likely to experience insufficient iron intake or iron-deficiency anemia, which can show up as persistent tiredness, weakness and difficulty concentrating.
- Low B12 and folate. They are both essential for making healthy red blood cells, which transport oxygen through your body. Because vitamin B12 is naturally found almost exclusively in animal-derived foods, if you follow a vegetarian or vegan diet, you may consider eating fortified foods, supplementation or occasional animal-based sources like meat, eggs and dairy.
- A heavily plant-based diet (without planning). Plant foods can absolutely be part of a healthy low carb lifestyle, but the non-heme iron in plant foods is absorbed far less efficiently than the heme iron found in meat. And plants do not provide vitamin B12, which is one reason plant-forward eaters need to pay closer attention to their iron and B12 levels.
TIP: If you're feeling persistently tired despite eating well, ask your doctor for a simple blood panel checking iron, ferritin, B12 and folate. There are several different types of anemia so its important to look at more than just iron. It's a quick way to rule out (or catch) a fixable cause of fatigue.
The Nutrients That Turn Food into Fuel
Eating the right foods is half the equation. The other half is having the nutrients on hand to convert what you eat into usable energy at the cellular level. These stand out:
- Carnitine. This compound is the literal shuttle system for fat metabolism—it transports fatty acids into your cells' mitochondria, where they're burned for fuel. For a low carb eater relying more heavily on fat for fuel, having enough carnitine on board matters. Carnitine is found in its highest concentrations in red meat, with smaller amounts in poultry, fish and milk, so regularly including these foods helps keep this energy-conversion pathway running smoothly.
- Creatine. Best known in fitness circles, creatine's job is more fundamental than muscle building. Creatine helps supply energy to all your body's cells, primarily muscle cells, by providing the energy needed to regenerate adenosine triphosphate (ATP), the fuel your cells use for basic functions, muscle movements and overall energy, during periods of high energy demand. Found naturally in red meat and fish, you’d have to eat more than 2 pounds of meat or fish to achieve the commonly recommended 5-gram dose. Research suggests supplementation is a safe and effective option.
- CoQ10: A nutrient that may support energy production and is also a fat-soluble antioxidant, protecting your body from free radical damage and oxidative stress. While your body produces it naturally, levels decline as you age, which is where supplementation may be an option.
Eating—and Meal Timing—For Lasting Energy
Sustained energy isn't only about what you eat. When you eat matters too. This is where low carb eating, intermittent fasting and circadian-aligned eating work together.
- Front-load your meals. Your body is more insulin-sensitive earlier in the day, meaning it processes nutrients more efficiently in the morning and early afternoon. Eating more of your carbs earlier in your eating window sets you up for steadier energy through the day.
- Give your body a nightly break. Digestion naturally slows in the evening. Finishing dinner earlier (ideally before 7 p.m.) and fasting overnight, gives your digestive system a rest and aligns with your body's natural rhythms, rather than working against them.
- Keep meal timing consistent. Eating around the same time each day helps stabilize hunger-and-energy hormones like insulin, ghrelin and cortisol, so you're less likely to hit unpredictable energy dips.
- It's "Low Carb" not "No Carb." With this mindset, success becomes less about eliminating carbohydrate-containing foods altogether and more about being intentional with portions, while limiting excess calories from refined grains and added sugars.
TIP: Combining a low carb lifestyle with circadian-aligned eating helps you tap into your body's natural biology for metabolic resilience and lasting energy.
This same "right carbs, right time" principle extends to your overall carb strategy: pairing quality carbs with protein and healthy fat and leaning into more of them earlier in the day when your body can use them most efficiently.
Learn more: Circadian Rhythms and Low Carb Eating
Energy-Boosting Foods to Build Your Plate Around
Stock your kitchen with foods that support sustained energy:
- Red meat and poultry: Natural sources of carnitine, creatine, iron and B12
- Eggs: A complete protein with B12 and choline for brain energy
- Fatty fish (salmon, sardines): Protein, B12 and anti-inflammatory fats
- Avocado: Potassium, magnesium, fiber and healthy fats, which are digested more slowly than simple carbs
- Leafy greens (spinach, kale): Folate and non-heme iron
- Nuts and seeds: Healthy fats and magnesium, which support ATP production
- Greek yogurt and cottage cheese: Casein protein, which is absorbed more slowly than whey for sustained energy release, plus B12
- Berries: Fiber and antioxidants without the blood sugar spike of higher-sugar fruits
The Secret to Lasting Energy
You create sustained energy, meal by meal, through steady blood sugar, the right nutrients and eating patterns that work with your biology instead of against it. By focusing on quality protein and low glycemic carbs, watching for common nutrient gaps, and aligning your eating with your body's natural rhythms, you can trade the blood sugar rollercoaster for energy that lasts.
Jon Clinthorne, PhD
Sr. Director of Nutrition