Weighing yourself immediately after a meal can also produce false scale readings. An average-sized meal can easily weigh a couple of pounds, which is what you'll seem to have gained if you jump on the scale right after your meal. That's because the scale registers the weight of the food, not the weight you will have gained from the meal - plus any water-weight gain from excess sodium.

Of course, after the food is digested it will stockpile some extra calories, but keep in mind that it takes 3500 calories more than your body needs to gain one pound of weight. So, if you've eaten a heavy meal and the scale registers a four-pound weight gain, for that to be accurate, the meal would have to equal at least 14,000 calories. That's like eating 8-12 whole pizzas, 23 Big Macs, or 56 bowls of pasta marinara!

Exercise rarely contributes to an increased weight on the scale. Although the argument that muscle weighs more than fat is often used to explain weight gain when you increase physical activity, in truth, the effects of weight training on your overall weight are marginal - about one pound a month is the maximum increase. So don't be fooled into thinking that weight gain is a by-product of exercise. More likely, it is true weight gain or a by-product of water retention.

Although small, day-to-day fluctuations are not a reliable reflection of weight loss or gain, the scale can be an effective long-term indicator of weight loss, especially when used in conjunction with other methods of assessing weight. 

Pat Fiducia suggests these tips to help you use your scale effectively:

• Understand the scale's limitations. Keep in mind what the scale can and can't do. Remember that normal and significant fluctuations can occur through water retention, water loss, glycogen storage, changes in body mass, and the normal ebb and flow of fluids.
  
  
• Focus on what you want to accomplish. Losing body fat and increasing lean muscle mass is your primary weight-loss goal. Remember, it is impossible to change body fat significantly in a day or two, or even a week, so don't allow your moods to be contingent on the scale.
  
  
•  Don't weigh in daily. The scale should be used to monitor weight trends, not day-to-day weight fluctuations. Weigh in once a week or less and chart your progress over time. It's also best not to weigh yourself for several hours after eating. For more accurate weigh-ins, weigh yourself first thing in the morning before eating.
  
  
• Think outside the scale. Think about how you look and feel, how your clothes fit, your frame of mind, your energy levels. These things should be as important as the number on the scale.
  
  
• Monitor other indicators of success such as your blood pressure, your cholesterol levels, and your glucose levels. Measure success by the positive changes you are making. Noting skin-folds or body measurements can also provide some more accurate numerical charting of fat loss.
  
  
• Pay attention over time. While small daily fluctuations should not influence you significantly, pay attention to larger losses or gains over time (weeks and months). The scale is still a reliable way to gauge fluctuations over longer periods of time.