When I do my work-out in the morning right after breakfast (which consists of a 100-calorie yogurt), I am always really tired easily, I feel as though I don't have a lot of energy and have problems doing my work-out routine much more than if I work-out in the evening after supper. What could be the cause ? I'd like to exercise in the morning instead of the evening but I just feel like I've got no energy, what could I do ?

I think you're tired because you definitely need more food energy than that to fuel your morning workouts. Do you have a post-workout meal? What does your workout consist of?

I don't come alive until evening myself, although I have to wake up every morning bright and early. Since evening workouts don't interfere with my sleep I opt to move it at night.

Maybe you should eat a little snack before exercising. Most likely, you don't have any fuel available to perform your workout since you've been fasting for many hours. A little protein mixed with a small amount of complex carbs should do it. You could be dehydrated as well.

Also, have you been checked for diabetes or hypoglycemia?

I don't have diabetes or hypoglycemia, no. I usually eat an Activia yogurt in the morning so I get around 100 calories before I work-out. I generally eat dinner post work-out.

My workout consists of walking fast at 3,7 for 45 min although I run at 6 during 1 min every 5 min during the first 30 minutes.

I think you need more calories. Eating yogurt pre-workout is fine. But waht about after your workout? You need to refuel your body with something after you have worked out so you can gain more energy. Protein or even some carbs shouls help bring that energy back.

I don't agree that one needs more food to fuel the energy. I routinely run on my treadmill in the early a.m. and I only drink a bit of water prior to that. I am on it for 65 minutes and I am just fine. Any food in my stomach prior to exercising does not suit with me. I think everybody is different and needs to find whatever it it that works for her/him.

^ Right on Tomato, I totally agree.

I just assumed things and everyone knows that's bad. The way I read the original question was that breakfast is 100 calories. I assumed that was it, nothing more until lunch. For me, if I had 100 calories for an early breakfast, had a workout and nothing more until lunch I'd bonk too.

I too often exercise on an empty stomach, as a pre-workout meal doesn't agree with me. I'd so be sick. But, like I said, I exercise at night. I do it before dinner but have the fuel of my other meals throughout the day.

Well I eat breakfast at 9 am and exercise at like 9:30 or 10:00 until (I sometimes do take small breaks so it's more than a 45 minutes work-out) maybe 11:30 am where I will eat dinner.

You need to mix the yogurt with a protein i.e boiled egg or something because you are burning off more calories then you are intaking therefore resulting in low blood sugar. By the time you finish exercising its as if you've exercized on an empty stomach.

The protein will help stablize your blood sugar

Eating more might be a good idea, but yogurt already has protein.

im on the low glycemic index diet for pre-diabetes and hypoglycemia and my doctor told me to always eat a protein in addition to a yogurt that yogurt is not enough.

Ah, I see. However, we don't know if the OP is on the same type of diet. She may just be needing more calories--not just more protein. In that case, an egg white isn't going to be much assistance.

Are you getting enough sleep when you exercise in the morning? Normally when I exercise in the morning, I am more alert during the day.

I workout in the mornings before I eat. I always feel fine, but like other people said, just listen to your body. You may need to eat something more.