Losing weight is hard, but maintaining weight loss is even harder. If you can't maintain your weight loss, there's no health benefit and in fact it may actually be more harmful to your health to lose and gain weight over and over again (yo-yo dieting) than to never lose the weight in the first place.

Losing weight is really just simple math... use more energy than you eat and you'll lose weight. To estimate how many calories you need, multiply your weigh in pounds by 13, if you're not very active, and 15 if you're active. For example, a 160 lb man who isn't very active would need 2080 calories per day (160 x 13) to maintain his current weight.

A pound of fat equals 3500 calories. Therefore, if you eat 500 fewer calories than you burn each day, you'll lose 1 pound a week. Note that there are two sides to this... calories eaten and calories used by your body. You can work on either one, but eating less AND increasing physical activity is most effective.

The National Weight Control Registry consists of over 4000 individuals who have lost at least 30 lbs AND maintained their weight loss for over a year. Data from these individuals indicates that they have been able to maintain their weight loss by limiting the fat in their diets AND exercising regularly.

Each year prior to the holidays, I see many tips for avoiding holiday weight gain. While it certainly doesn't make sense to pig out over the holidays, it's not what you eat on a couple special occasions that causes long-term weight gain.

I gain 5 lbs every Christmas, mostly because my grandmother and aunt bake about 10 different kinds of amazing cookies. I rarely have access to homemade cookies, so I thoroughly enjoy them over the holidays. When I return home from the holidays, I return to my normal eating habits and my "cookie weight" is gone by mid-January.

It's what you eat day in and day out that really matters. A candy bar from the vending machine at work every afternoon adds up to 50,000 calories (200 calories x 240 work days) over a year! This alone could cause you to gain 14 lbs per year!

The Best Diet?
What is the best weight loss diet? This might surprise you, but I recommend a diet based on what you're currently eating. You may be thinking "hey, but my current diet is what got me into trouble". However, unless your diet is unbelievably horrible, it makes more sense to improve your current diet than to try to adopt an entirely new eating style that you're unlikely to stick with.

To lose a pound a week, you'll need to shave 500 calories off your daily diet. Here's some suggestions:

• Trim the fat. Fat is the most concentrated source of calories in our diet (9 calories/gram compared to 4 for protein and carbohydrate). Look at your current diet and identify lower fat options for foods you currently eat. This could include low-fat version of milk, cheese, ice cream, sour cream, and salad dressings. Choose lower fat meats, such as skinless chicken or fish, instead of beef and pork. Avoid fried foods, such as french fries, tortilla chips, and chicken nuggets.
  
  
• Cut out one of your daily "junk" food snacks. This could be a morning donut, lunchtime potato chips, afternoon soda, or evening cookies and ice cream. This alone can reduce 200 or more calories.
  
  
• Increase fruits and vegetables. Fruits and vegetables provide important nutrients without many calories and the fiber will help you feel full.
  
  
• Watch your portion sizes, especially when eating out. If you feel stuffed after you eat, you've eaten too much. Stop sooner next time.

In addition to diet modifications, adding 30 minutes of walking or other physical activity to your daily routine will burn another 200 calories. You'll lose weight faster and be more likely to keep it off.

Losing 1-2 pounds of weight per week is a reasonable goal. Any faster than that and you're going to be very hungry and your metabolism may actually slow down causing you to burn fewer calories than usual.

What About Low-Carb Diets?
Most of us know someone who has lost weight on a low-carb diet. Low-carb diets work, at least initially, because they limit the consumption of the major nutrient group in our diet.

If you think you could follow a low-carb diet for the rest of your life, you might want to think again. The world is full of carbs, it's going to be really hard to avoid them forever. Do you really want to go without pizza or birthday cake forever? Plus, believe-it-or-not you will get sick of steak, bacon, butter and eggs!

My son's football coach went on a low-carb diet last year and lost almost 30 lbs. He thought it was great, because he lost 12 lbs in the first week (first red flag), but then he said he'd slipped a bit recently and gained 5 lbs in a week (second reg flag).

First of all the only way you're going to lose 12 lbs of fat in a week is if you're climbing Mt. Everest and forget to bring any food! What's the explanation for the quick weight loss many people experience on low-carb diets? It's very simple... high protein diets cause you to urinate a lot, so you lose water.

Your body is mostly water and water is heavy (about 8 lbs per gallon). When you lose water quickly, you'll feel lighter and your waist may be noticeably smaller. However, as soon as you eat normally again, your body will rehydrate and you'll gain weight.

If you still want to try a low-carb approach, try one of the more sensible plans. The main thing to look at is what carbs the plan wants you to eliminate. Some low-carb plans limit all carbohydrates, including fruits, vegetables and whole-grains. That's just dumb and potentially harmful.

A low-carb diet that allows "good" carbs (fruits, vegetables and whole grains), but limits carbs that are lower in nutrition and often eaten excessively, such as refined sugars and white flour, is a better approach. However, it's still going to be difficult for most people to stick with long-term.

Another important consideration is the amount of fat, particularly saturated fat in a low-carb diet plan. Some low-carb plans allow unlimited consumption of meat, dairy and eggs. The problem is that all these foods are high in saturated fats and saturated fats are a major risk factor for heart disease.

Keep in mind that being overweight is also a risk factor for heart disease. If you're overweight and start eating a diet that's high in saturated fats, it's a double whammy for your heart. Although research has not shown that low-carb diets are harmful in the short-term, the long-term effects are unknown.

The only diet worth trying is one you can stick with for the rest of your life.

Relatively small weight losses (10 lbs) can significantly reduce your risk of disease.

It's better to be fit and fat than thin and unfit.