Go into any exercise supplement store and you'll be hit with shelf after shelf after shelf of powders and pills, all promising transformative results. And if you're to believe their sales pitches, you really ought to be spending half your paycheck on a suite of different products if you really want to maximize your time in the gym.

Here's what they don't tell you:

• There's no substitute for working out and eating right, and that anything else is just icing on the cake. Those tubs of mystery powder aren't magic bullets.

• Since supplement manufacturers aren't required to get their products approved by the FDA before hawking them to you, there's no real guarantee that anything works like it says it does, or is safe to consume in the first place.

• The vast majority of products on supplement shop shelves are completely useless for the vast majority of people.

Now, all that said, there are a very select few that are well understood, safely produced, and actually worth taking. They're not going to work miracles, and they're not right for everyone, but if you're serious about getting into shape, they'll be a small help.

Whey Protein

This is the supplement you'll see around most often. It comes in those big plastic jugs in all kinds of flavors, and is a favorite of weightlifters the world over.

What Is It?

Basically, it's a byproduct of milk. When milk is intentionally curdled to make cheese, the curds are separated from the liquid whey, which is then processed further into a powder. That powder is very high in protein, and relatively low in calories, so it's useful if you're trying to build muscle but have a hard time eating enough protein from other sources.

To build muscle, you should be eating about .75 g of protein per pound of bodyweight. Some people say 1 g/lb or more, but others still say that's actually overkill – there are lots of studies out there you can read up on to make your own informed decision. But if you go with the .75 g number, which is a safe bet, that's 135 g of protein per day for a 180 lb person. If you have a big appetite and tend to eat a lot of meat, that's pretty easy to do with just food. But if you have a hard time consuming that much protein in your typical diet, that's where whey protein powder comes into play.

Add a couple scoops to a glass of water, milk, or cold-brewed coffee, and boom: you've got an easy extra shot of protein for the day.

The Bottom Line

Is it necessary? Hell no. But if you want to maintain a high protein intake for muscle building, and struggle to eat enough to hit that goal, whey protein is helpful.

Creatine

This is widely considered the most well-studied exercise supplement out there. It's a powder, easily dissolvable in water or a protein shake, that you take about 5 g of (roughly a spoonful) per day.

What Is It?

An organic acid, naturally produced by the body, that helps to supply energy to muscles. It's most closely linked with short, high-intensity movements, like sprinting or weightlifting.

While you get a certain amount of it naturally from food and bodily processes, adding a little more into your system has been proven to help with performance in the weight room. It won't turn you into a powerlifter overnight, but creatine has been shown to modestly increase strength, both the max amount of weight you can lift and the number of reps you can do.

It's also said to increase the body's water retention, causing slight weight gain (about 2–5lbs). Bodybuilders often say this makes them look more muscular, but it could be a disadvantage if, say, you're training for a boxing match with a strict weight limit.

The Bottom Line

It's cheap, it's simple, and it works. Given the well-established track record (beneficial strength effects have been proven in hundreds of studies), it's worth taking for anyone interested in maximizing their weightlifting abilities.

Caffeine

That's right, plain old caffeine. There are all kinds of "pre-workout" drink mixes out there that promise increased energy and focus for a workout, but the only really effective ingredient they all share is this stuff.

What Is It?

A stimulant for the central nervous system. As anyone who's ever had coffee before knows, it jolts you awake and aids concentration, especially early in the morning when you're tired and grumpy.

As far as exercise is concerned, it can kick-start your workout on days when you're feeling lethargic. It's especially helpful if you work out early in the morning – a 5 am alarm is a lot easier to manage if you have a quick hit of caffeine at the ready to get you out of bed and into your workout gear. And once you're ready to lift, a caffeine rush can give you a more intense, focused gym session.

You can get it the old-fashioned way – a cup of black coffee, or a sugary energy drink – or you can buy caffeine in pill form. Just be very careful not to overdo it. It depends on your tolerance, but for most people, 100–200 mg is the sweet spot (for reference, a small cup of coffee is about 100 mg), and going too far beyond that will leave you jittery and nauseous.

The Bottom Line

If you have a hard time dragging yourself to the gym, especially early in the morning, this can be a godsend. It wakes you up, increases focus, and can provide minor strength benefits. Just don't take too much.

Give those a shot and see where they take you. Just remember: you can't supplement your way around hard work.