Definitely try some exercise. It sounds counter-intuitive - you have no energy, and exercise tires you out, so why should you have more energy by exercising? But wait about a half hour after you finish exercising, and the rush comes (well, it's not so much a rush as it is a little ripple of change). You'll feel noticeably happier, and more willing to plan things and do your chores, and you just feel more involved in life. Wait a week or so, and you'll notice just how much more you're doing, and after a few weeks, that lethargic feeling will be gone.

I used to sit around the house, not have much interest in doing things, and vaguely plan to clean my room... someday. I've been exercising for three weeks now, and I've cleaned just about everything in the apartment, I feel happier, I want to get up and rearrange things, and I'm more engaged in what I want to do. You can read my blog about my goal to exercise more here. I'm doing a sort of "Julie & Julia" type deal, where I blog about my experience with exercise. I'd like to try it for the next year, just to see what happens. Coming up on month one. :)

I've got a medium to mild-ish version of chronic fatigue syndrome (CFS), a condition which through the years and in various places has also variously been known as chronic fatigue immune dysfunction syndrome (CFIDS), myalgic encephalitis (ME), Royal Free Disease, Post-Viral Fatigue Syndrome, (PVFS), Yuppie Flu, Tapanui flu.... in historical books, a condition called neurasthenia is thought to have described people suffering a similar condition in the past.

http://en.wikipedia.org/wiki/Chronic_fatigue_syndrome
http://www.cfs-news.org/
http://www.endfatigue.com/resources/index.html

I thought I'd mention this as when I first started suffering, I was just extremely tired and thought, "What on earth is wrong with me?" I felt noticeably different to the way I had felt before, and had just gotten over an unusually severe mononucleosis/ glandular fever kind of flu. (Well.... not really "gotten over"... the acute flu symptoms had basically finished, but I simply had not gone back to normal in a lot of ways.) It doesn't always have to have a flu onset, but this is often a way that it begins. Millions of people get a flu or mono, (often caused by viruses such as Epstein-Barr - EBV - or cytomegalovirus - CMV), get over it, and carry on exactly as they were before. (Some fight off these viruses without ever seeing any overt symptoms.) In a few people, though, it seems that they are already run-down in some way or their physiology just sensitive at that time for some reason - and the body goes into an unusual postviral fatigue state. As mentioned, a viral beginning is not the only way of it starting.

"Lazy", as you say - this was the hardest part - convincing myself, and then others, that it was NOT just laziness or lack of motivation. I had never been particularly lazy or unmotivated before; in fact I was always a very hardworking person and actually pushed myself too much quite often, which I believe was a factor in making me vulnerable to the condition - on top of a lot of stress from lots of different sources at that time.

I think knowing what your situation is would be a helpful first step, so if you have the resources to do so, it would be worth getting some tests done - even just to first rule out something more serious, for your peace of mind. Take care to only accept answers that are sensible, informed, forward-thinking, balanced, and not some sort of way of talking you out of a great deal of money for an unproven "cure". It's unfortunate that I have heard that depending on the actual experience and up-to-dateness of which general doctor you talk to, you can easily be sent away with antidepressants or a referral to a psychiatrist/psychologist/therapist/counselor, when that is not the problem. I'm not saying that these problems aren't real and can't cause these symptoms at times. But it would be unfortunate to have this band-aid solution put on chronic fatigue syndrome or fibromyalgia - or even worse, a serious medical problem that needs urgent attention.

I haven't found a "cure" for my chronic fatigue - and don't worry, it isn't life-threatening. It can just be rather life-altering. :) Don't panic - Many people feel terrible for six months, a year, or a couple of years, then find that they return to normal. For others like me it becomes a way of life, and you just have to adjust to the change. My first year I was actually pretty bad, but I only spent my first year feeling exhausted and ill enough to sleep hours through many days and nights - I almost slept a whole year away, really. After that, I improved a lot and have just plateau'd at "Quite physically tired a lot of the time but can do most of what's really important to me, with some lifestyle adjustments." Many, many people get a much better improvement or full improvement.

Some will swear that some supplement, homeopathy, vitamin, naturopathy, etc have cured them or improved them a lot. It seems to be extremely variable - the experiences people have had and what has helped. A sleep clinic may be useful as it's thought that changes in sleep quality may be involved for some. There is one doctor, Dr Jacob Teitelbaum M.D., who seems to be at the forefront of the research and treatment options. He does have a range of supplements that are everything that will supposedly help the most in the easiest form to take - however, they are supported by clinical research and as far as I remember, he doesn't profit from them. He just wanted to put it all together for his patients to take easily.

http://www.endfatigue.com/about-dr-t/Index.html

I think the biggest thing I can suggest is read and educate yourself. I have tried a great deal of different treatments with varying success. Nothing has made the problem "go away", but through my reading I've found things that definitely made a difference and supported me.

Some of my suggestions are - (and these may be very helpful even if you find that CFS or a recognizable medical syndrome isn't your problem):

- A really good, high-quality supplement with a very generous amount of easily-absorbed magnesium. Magnesium, as well as a few other chemicals and compounds, is one of the things that they are definitely sure is involved with tiredness, normal energy production, muscle cramps/soreness and muscle fatigue, etc.

http://findarticles.com/p/articles/mi_m0ISW/is_247-248/ai_113806998/

I just started using a powder supplement with over 300mg elemental magnesium per dose, as magnesium amino acid chelate, magnesium aspartate, and magnesium orotate. It also contains lots of other things that are said to be important in absorbing it and using it properly. I have noticed quite a difference already. I had always made sure I took a "multivitamin" with magnesium before, but sometimes for a particular problem I guess that's not enough.

- At one stage, I felt Alpha Lipoic Acid was helping me a lot - when I tried another brand later, I didn't notice anything. Who knows. Dr Teitelbaum's book covers every therapy and supplement I have ever heard of and not heard of, so it's worth looking over it.

- Some people swear by homeopathic treatments, vitamin injections from your practitioner, acupuncture... the list goes on. Some people even feel quite a difference with one of those big vitamin B/C/Magnesium tablets that you dissolve in water. I even get a boost from those.

- I find that stress is the single biggest factor that influences me. We can't all "banish" stress - but part of the time I've spent at a lower level of activity, I have used to read and learn a ton about mental wellbeing, psychology, etc. Very very valuable in a lot of people's cases, even if you don't officially have some sort of physical syndrome. Again - read all about it! This kind of material often has a lot to say about motivational techniques, too - helpful for those who find that they are just feeling a bit flat, and a bit "blah" for either a medical or non-medical reason. The mind and the body are, of course, connected. If you think anxiety, depression, perfectionism, or something similar may have run you down, I recommend the work of David Burns.

http://www.feelinggood.com/

There's certainly something to be said for manageable exercise - this has been used incrementally to treat chronic fatigue, I'm not sure how it works for those who are so severe that they are bedridden and need a wheelchair. Definitely something to try though, as others have mentioned. I try to regularly do a little, but sometimes it really is a choice between - Do I do some exercise, then collapse into bed the rest of the day? Or do I not exercise, and get something done?..... It's a tricky one!

Finally, here's a little list of tips I found for improving stamina for ordinary people. I think there are some good ideas here that some busy people may have overlooked - including taking quality time for yourself to recharge your batteries and feel more balanced; staying connected with others; yoga; and meditation.

http://www.parentree.in/Parentree-editors/journal-1629/11-ways-to-increase-stamina-and-energy---for-moms.html

Best of luck, it's no fun struggling to keep up with what you used to do quite easily!

At the very least, get up and walk around, or do something to get blood flowing. I sit all day at work. When I get tired, you know that time around 2 in the afternoon, I stretch when management are looking, and when they aren't I walk around for a little bit, just long enough to wake me up. Then it's back to work.
If you have time you should really exercise, even if its 20 minutes a day. Get your heart rate up, eat well, and you'll find energy again.

Any change in normal energy levels can certainly be a sign of a medical problem, so don't be shy about consulting your Dr. Just the fact that you mention that in your question could be your subconscious trying to tell you something.

That said, and without any where near enough background information to go on, I will share two of the most common causes of fatigue:

Not drinking enough water, and
Not getting enough physical activity.

Of course, depending on your overall health, you should consult your Dr before starting any major physical activity regimen, but often just a moderately brisk walk for 15 minutes a day can do the trick. (Moderate-brisk being the key.)

Also be sure you are consistently getting at least 7 hours of sleep per night, and try to determine if it's good sleep (with dreaming) and not problematic like having sleep apnea.

Hope this helps. If you're wondering about the Dr.....go!

Whereas exercise as stated is an excellent way to increase ones energy as it tones the body’s energy centres and making them function more efficiently. But there may be other factors for your energy loss, the lethargy etc that exercise alone will not address.

If after trying a good exercise routine, (I suggest the PACE system and Qi Gong/Tai Chi), you still feel a loss of energy and lethargy, then please post a new question indicating what you have tried or done to address the situation. If the suggested exercise routine does not help then other factors are at play.

Very good question by the way. A large part of the North American (Canada & USA) population suffers from diminished energy and the numbers are climbing. Let me/us know how you do.