A lot of topics in this post are complementary to (and some unavoidably redundant with) my post On Weight Loss in general. This is more geared for troubles you may encounter while doing so, and what you can do about it.
A common problem
For most of us normal people, energy is not something that comes by easily. A lot of the time, it's what prevents people from working out in the first place because day-to-day life is draining enough.
I've been in that situation many times; I usually fall off the proverbial horse at the waning time of each semester, and
just not having enough energy to exercise on a regular basis, so some knowledge in this post is stuff I learned the hard way.
I'm a pretty low-energy person most of the time. I'm very susceptible to "the blahs." I believe I have a naturally subpar metabolism, and as a result I'm a bit more lethargic and lazy than the average person. If you're like that too, I hope some helpful things from this post that I figured out the hard way.
Energy and metabolism go hand-in-hand. A higher metabolism means your body uses more energy, and therefore makes you more energetic. That explains why most naturally lean people seem to never run out of juice, and it seems a bit unfair at first considering that the ones who really need that energy are the ones who aren't naturally thin or athletic. However, there is good news: our metabolisms are not set, and fortunately we can do a few things to fire them up.
Sleep
I'm a night owl but I love to sleep. I'm definitely not a morning person; it takes forever to get going in the morning, and I will sleep 10 or 11 hours a night if I don't set an alarm.
Sleep is a huge factor in regulating energy levels. Not only does it need to be sufficient (it varies individually; some people only need 8 hours or less), but also somewhat consistent. This has a lot to do with hormones. When things get out of whack, your body will do what it can to fix that, usually by making you tired all the time.
Artificial light can really confuse your brain. So can a timezone shift. Ever had jet lag?
When I "fell off" the horse so to speak near the end of the semester, my sleep schedule and biorhythms were FUBAR. Some days I had 8 AM classes, and on others my day started at noon. I ended up staying up late all the time but taking naps on a regular basis; I discovered later that these long naps were ultimately not helping to regulate my hormones (the all-nighters didn't help, either). Power naps (< 30 minutes) are usually great because it gives you a boost of energy to help you take on the rest of the day without sending you into deep sleep and subsequently messing up your hormonal cycle.
Stress (the hormone cortisol) can be a real problem if it gets out of control. Having a regular and adequate sleep schedule can do very well to prevent this from happening, because cortisol is a really bad thing to have too much of. If you have chronically high levels of it, it can do a bunch of things to make you feel bad and kill your metabolism.
Nap minimally and sleep at fairly regular hours if you want to work with, rather than against, your hormones. To facilitate this goal, keep artificial light to a minimum when it gets late. It is worth noting, though, that getting in shape will often improve chronic medical conditions of all kinds.
Exercise
The ironic thing about exercise is that it actually increases your metabolism by a substantial amount for at least a day, but people (including myself) will still avoid it if they don't feel they have enough gas in the tank to do so. This explains, in part, the phenomena of getting on "the horse" or "the wagon."
Or, you can do both!
The degree of metabolism boost varies with type and intensity of exercise, but generally anaerobic (e.g., weightlifting) activity is much more effective than aerobic (e.g., plain cardio) exercise. This is tied to the fact that anaerobic exercise is superior for weight loss; a higher metabolism means more fat can be burned for energy. I've talked about this in detail in my past posts.
Food AND Exercise are crucial to success
Food is energy. It shouldn't surprise you that if you don't eat enough and don't exercise, your energy levels will drop. Your body likes to conserve energy, because it's a survival mechanism: eat less, burn less. It's quite good at conserving energy when there is a scarcity of food. "Calories in - Calories = Calories Lost/Gained" out is still valid (thanks to thermodynamics), but Calories out is a function of Calories in, among many other things. This is why dieting without exercise isn't very effective most of the time, and why "weight loss calculators" based on calorie intake almost never work. The energy balance becomes useless for calculations when you can't easily determine Calories out. Your body doesn't care that you want to lose weight; it just does its thing and isn't going to burn fat unless it has to. So if you diet and don't exercise, your metabolism will slow down. And when that happens, your energy levels will drop, you may feel like crap, and eventually it will get to the point where you won't have the energy to exercise, and your diet will ultimately "fail."
Fortunately, exercise will force your body to pump up your metabolism in spite of low energy intake from food. This is why both diet and exercise are needed for substantial fat loss.
On the flipside, too much exercise and not enough food will cause you to "burn out." Eating very few calories is not really "dangerous" but your body can only surrender so much fat in a day. When the caloric deficit becomes too large, your body will slow down and your energy will drop.
Consistency is key. I've said it before and I'll say it again: Livestrong.com's MyPlate is an excellent food tracker that I HIGHLY RECOMMEND if you're having trouble losing weight, or want to do things right the first time. If you're doing some form of exercise but not making progress, chances are that your diet needs work. Don't forget that protein is #1. Sometimes, meat is better than fruits or veggies as far as looking better is concerned.
Stimulants
So, let's say you're doing everything right, but you just don't have the drive to work out. If all else fails, stimulants are a surefire way to increase your energy and/or metabolism. Some people need them all the time; others just need it as an occasional boost.
Stimulants in a nutshell.
Of course there's the #1 drug in the world, caffeine, that some people depend on almost every day to get their day started. Sometimes, that's all it takes, but there's always more out there if it's not good enough for you.
As a lazy college student, I don't even bother:
200 mg pills are not recommended on an empty stomach.
Weight-loss supplements work by either increasing metabolic levels (Calories out), giving you enough energy to work out, or both. Some are better than others, and some (usually the overpriced ones that are advertised with outrageous claims) are crap. Some "pre-workout" stimulants (e.g., Jack3d, which I love) are great for shifting your metabolism into turbo mode; they do double-duty by making your workout more productive, and boosting your metabolism in general. The fat-loss stimulants which make a substantial difference are inevitably very powerful, and erroneously seen as dangerous in most cases. The infamous ephredrine was banned because it was effective and subsequently abused once it became popular; not because there is something inherently dangerous about it.
There are some other mental hacks you can do that help you to make exercise not a drudgingly painful experience; I'll talk about that and some relevant psychology in an upcoming post.
TL;DR
The key to energy and subsequently improving your body? Get your sleep, balance your food and exercise, and take stimulants if you need or want an extra boost.
