If you have just started keto and intermittent fasting, chances are your body has not really adapted to using fat for energy instead of sugar so it is still in this transition phase which will make you feel tired and irritable. Just keep going and make sure you add more healthy fats to your meals and this will go away within few days.
If you’ve been on keto for a while and you still feel tired with no energy, then you might not be consuming enough sodium so you’ll have to add more sea-salt or Himalayan pink salt to your diet. When you avoid the grains on keto the need for sodium goes up so you need to make sure you are providing your body with enough salt. A good way to do this is to consume only 1/2 tsp of sea-salt or pink salt with water everyday and the rest you’ll get it from food cause on keto you need around 1 tsp of salt per day.
Other reasons you could be tired on keto is a lack of B vitamins so you need to make sure you are providing your body with the needed B vitamins from a natural source like Nutritional Yeast. A good way is to consume 2-3 tbsp of nutritional yeast everyday.
Make sure you are providing your body with all the electrolytes (potassium, sodium, magnesium…) especially potassium because we need that in large amounts everyday (4700 mg per day). So you’ll have to consume large amounts of high quality vegetables like kale, broccoli, cauliflower, celery, parsley, spinach, cabbage, Swiss chard, arugula…
Also make sure you are not consuming hidden carbs or bad ingredients that could be keeping you away from deep ketosis or maybe completely out of ketosis like “maltodextrin”, “dextrose”, “maltitol”, “corn starch”, “high fructose corn syrup”…
And lastly, if you have recently added intermittent fasting and you are feeling tired and sleepy going from one meal to the other, chances are your blood sugars are getting really low and your adrenals are not adapting quite well to stabilize your blood sugars level. You’ll have to back off a little and start gradually with intermittent fasting. Maybe you go back to 3 meals per day, no snacks, then you go gradually to 2 meals. Consuming nutritional yeast will greatly support your adrenals and will improve your situation.