As one year flips over into the next, you're finally flipping your life over and making lasting dietary and lifestyle changes. It's all in the pursuit of a better, healthier you. But what makes this year any different from all those others?

It's simple: This is the year you're not going to make any of these classic mistake that have turned too many January dreams into March regrets.

1. Starting Too Fast

The single most vicious diet mistake is cutting calories too steeply, too quickly. The reason: Your metabolism—the baseline number of calories you burn over the course of a day—is constantly changing. It adapts to your current level of food intake and exercise.

So sure, you may initially lose weight rapidly by eating nothing but lettuce day in and day out. However, at some point, your metabolism and body will catch up to your reduced caloric intake. The adaptability of your metabolism is an inherent survival mechanism to ensure that your body conserves as much energy as possible when not taking in enough.

Be like the tortoise, not the hare.

Once your metabolism slows to match a reduced food intake, your weight loss will begin to plateau. The next logical step is to either further reduce intake or increase energy expenditure through exercise. The major problem at this point is that you're already eating very little, so throwing hours of cardio on top of that may not yield results, and will leave you feeling like a zombie! It literally becomes dangerous to further reduce intake, and there's simply not enough energy, not to mention time in the day, to increase exercise even further.

Alongside a drop in metabolism, your appetite becomes more voracious by the minute, and eventually you'll succumb, often taking in a buffet-style meal for the next few days. Remember, though, your metabolism has already significantly slowed, so those extra calories you eat are primed to be stored as fat. Before you know it, you're back at your prediet weight, if not heavier, because your body cannot keep up with excess calorie intake.

Solution

Be like the tortoise, not the hare. Start with small reductions in food intake, and gradually increase exercise. Monitor your progress using a combination of the scale, progress pictures, and energy levels—that last one often gets overlooked—and adjust nutrition and exercise accordingly.

This deliberate approach will allow you to maintain your sanity and satiety without losing muscle or control over your meals.

2. Having Unrealistic Expectations

Aiming to lose 50 pounds is an awesome target, but don't expect it to fall off in a few weeks, or even a few months. Losing weight too quickly sets you up for significant muscle loss and a metabolism operating at sloth-like speed.

Similarly, there's no magic program that will endow you with 20 pounds of new muscle in the next few months either—it just isn't going to happen. The body doesn't create muscle that quickly, no matter how much you try to eat.

Bodybuilders have taken years—decades, in some cases—to put that amount of muscle on their frame.

Solution

Understand the difference between positive thinking and realistic thinking. A general guideline to follow is the "1-2 pound rule." This guideline implies that you should aim to lose or gain no more than 1-2 pounds per week.

Lose any faster, and you're most likely losing muscle mass as well. Gain any faster, and you're probably gaining significant amounts of body fat, too.

3. Failing To Set Goals

Goal setting is vastly underutilized. Sure, you want to lose weight this year—that's great! But there's more to goal setting than simply saying, "I want to..."

Setting S.M.A.R.T. goals harnesses your focus and motivation to continue working on the task at hand, which in this case is losing or gaining weight. The acronym stands for "specific," "measureable," "attainable," "realistic," and "time-bound." Your end date serves as a great point to evaluate both progress and your approach, allowing you to fine-tune it to continue moving in the right direction.

Once you've outlined your ultimate goals, go back and develop short-term goals to help keep you on track throughout your journey.

Solution

Once you've outlined your ultimate goals, go back and develop short-term goals to help keep you on track throughout your journey. Refer back to them frequently for consistent motivation and to adapt your game plan.

Don't just rely on the moment of inspiration and your end date to guide you! Consider posting your goals in plain view, like on the refrigerator, so that you can refer to them daily.

4. Surrendering Too Soon

If weight loss were easy, obesity wouldn't be the problem it is today! No matter how right-on your approach, there will be weeks when you don't lose weight. That's okay. It's quite possible you're gaining muscle and losing fat, which won't be reflected on the scale.

On the other hand, as much as we might wish otherwise, muscle gain isn't linear—it often happens in bursts. Your body has to be subjected to enough of a challenging, consistent stimulus that it feels compelled to respond, and everyone's body will feel that at a different point.

Solution

Rome wasn't built in a day, and your ideal physique won't be either. Trust the process and embrace the grind. You will undoubtedly face obstacles, but these obstacles will make you stronger and make goal achievement that much more rewarding.

In the meantime, be patient and stick it out. A well-designed plan will set you up for success as long as you're putting in 100 percent effort in the kitchen and weight room.

5. Not Sharing Your Goals

I understand the urge to keep your fitness aspirations secret. Maybe you don't want people to think you're vain or selfish, or show that you're unhappy with the way things are now. My response is that this is far too important of a journey not to have a group in your corner.

If you don't share those goals, you're also missing out on one of the most effective forms of motivation there is: public accountability. Nobody wants to be that person who says they're going to do something, and then totally flakes. It may sound shallow to keep going to "show them," but for many people, it flat-out works.

If you don't share those goals, you're also missing out on one of the most effective forms of motivation there is: public accountability.

Solution

Tell loved ones, friends, and family about your goals. Not only will they provide an extra boost in motivation, but the extra accountability will keep you on track. And hey, it may even motivate them to make a change for the better in their own lives. But really, that's up to them.

In the meantime, consider getting involved in an online community, like the one on BodySpace. People who share your interest and have been where you're at will give you what you need to stay the course!