The Real Reason Your Diet Is Making You Tired

If you've been trying to stick to a specific diet, whether you're eliminating certain food groups or simply trying to limit your overall caloric intake, you may have noticed that after a few weeks, you're feeling more tired than usual. There are a few causes, ranging from side effects of the diet, if you're trying a low-carb or keto diet, to stress brought on by sticking to a tough diet, to simply not getting enough calories to fuel your daily living. 

Diets that require cutting carbohydrates may cause fatigue, especially at first, as your body adapts for the first week. Commonly referred to as the "keto flu," the period of adaptation your body undergoes as it shifts from burning carbohydrates for fuel and into fat-burning can make a person feel fatigued and even ill. Make sure you're eating enough calories despite your lack of carbohydrates, and that you're staying hydrated. The feeling should begin to fade as your body gets used to your new diet regimen (via Harvard Health Publishing). 

Your tired feelings may also be more mental than physical: If you're stressing about your diet and struggling to stick with it, you may be causing a rise in cortisol levels. This stress hormone triggers your fight-or-flight reaction, which can leave you feeling exhausted by the end of the day. You may even start to feel a tiredness that goes hand-in-hand with depression, especially if you're not achieving your weight-loss goals (via Verywell Fit).

Even a diet that seems extremely healthy can make you feel tired, if it doesn't contain enough calories to sustain you throughout the day. Salads for every meal might contain plenty of great nutrients, but if they don't contain many calories — otherwise known as energy for your body to function — you might find that you're unable to stay alert or feel exhausted despite not doing much physical activity. As you lower the energy you're taking in, your body lowers its metabolism — the rate at which it burns fuel — which can make you feel tired (via Healthline). 

You may even be eating enough calories, but if you're intermittent fasting — not eating for large portions of the day, then taking in all of your calories within a small window of time — your blood sugar may have dropped and you might simply need to spread out your meals throughout the day (via CNN).