When people are ready to start make an adjustment to their body, they choose the go-to phrase: "I need to lose some weight."
While they likely need to lose some weight, what they probably should say is, "I need to get in shape."
Just Losing Weight Can Be Bad
The term "losing weight" merely means to reduce the amount of pressure you put on the scale when you stand on it. The word "weight" does not differentiate between different components of your body, such as fat, muscle, bone, water, and organs. When you diet and/or exercise to "lose weight," you reduce the amount of fat, muscle, and water you have, and depending on how much you lose, it may negatively affect your organ and bone weight as well.
We can all agree that losing fat weight is a good thing (unless, of course, you are critically low on fat weight, see BMI vs BODY COMPOSITION for more information about low body fat %). Water weight is going to go from your body as you lose body tissue and improve your diet. However, unless you have spent years working out for muscle gains extremely hard, chances are you don't really have a desire to lose muscle weight.
If you focus too hard on just reducing your "weight," you will lose muscle; chances are way more muscle than you'd would be willing to give up just to change the scale's readout a little bit, if you were to sit down and think about it.
Overall Health Is More Important Than Overall Weight
When I say "getting fit," I mean:
When your fat% and muscle% are correct, what you weigh will be appropriate for your age, height, and gender. And what you weigh when you are "fit" may be considered too light or too heavy on the BMI scale, but BMI is merely a "first glance" technique designed for the first person screening you at the doctor's office, not a comprehensive medical or physiological diagnosis.
Getting fit can often also mean losing weight, but many people of already average weight or under weight might benefit from an adjustment in their fat% and muscle% - you can get more fit, too!
Getting Fit and Losing Weight
If getting fit also means losing weight for you, that likely means that you need to lose more pounds of fat mass than the pounds of muscle mass that you must gain to achieve your desired level of fitness.
Be careful to not neglect your needs to gain muscle weight while losing fat weight. Cardiovascular exercise (such as running, biking, swimming, Insanity, etc.) are great for making the scale show reduced pounds, but keep in mind that focusing on these types of routines makes you lose a lot of muscle mass at the same time!
Gaining Muscle While Losing Fat
Generally the two most important keys to most people's success at getting fit: Gaining Muscle and Losing Fat!
Cardiovascular exercise is indeed important to attaining a better level of fitness, but always focus on muscle gains at the same time.
I don't mean men building bigger biceps and pecs, I mean building muscle all over the body. Going to the gym and focusing on getting your arms ripped, your chest bulging, and your stomach into a 6-pack is only working a small percentage of the muscles in your body. You will look like a bodybuilder, but that's different than looking (or being) fit.
Find your appropriate body fat% and body muscle%, learn how to measure them, and work towards your goals towards fitness!
Losing Muscle Mass
Some people may actually need to lose muscle mass in order to achieve their goals. Several months or years of non-activity will lead primary muscles to increase in size, and secondary and supporting muscles to decrease and atrophy.
While cardiovascular workouts will decrease your primary muscle mass, you must work out your secondary and supporting muscles in order to provide joint strength and overall stability and fitness.
Balancing Your Muscles, a.k.a. Muscle Parity
In order to progress towards fitness, you must remember to work all of your muscles to achieve muscle parity (LINK), including your supporting and secondary muscles. Neglecting them leaves you unsteady when performing normal day-to-day activities; think about how it affects you when performing activities such as sports or fitness training. Working all of your muscles allows you to achieve all of your other fitness goals more quickly; your ability to perform all of your other workouts will improve dramatically.
Women, Don't be Scared of Building Some Muscle
Women must work four or five times harder than men to build the same muscle mass, and men have to work several hours a day to look like a bodybuilder.
You're in no danger of waking up one morning to discover you are suddenly "too buff" or have too much muscle mass - it takes an incredible amount of determination, an extremely specialized diet with nutritional supplements (usually involving steroids), and 20+ hours of exercise per week to do that.
If you're working out for less than 8 hours a week and you spend half of that on muscle building exercises, you will not build muscle too fast or look like a female bodybuilder; you will end up looking fit and healthy.
Instead of saying, "I'm losing weight," make a practice of saying, "I'm getting fit!"