Interpreting Your Weight Gain or Loss

InterpretingYour Weight Gain or Loss^*

How many times have you heard someone on a diet say, “This diet is great. I’ve lost two pounds since yesterday, and considering the amount of food I ate, I expected to gain weight.” Or, “I ate practically nothing today, yet I gained a pound. This diet doesn’t work.” The resulting elation or discouragement fails to take into account the normal fluctuations of weight having nothing to do with a gain or loss of body fat.

The truth is, your weight (scale reading) can easily vary by a few pounds over the course of a day even if you did not gain or lose any fat! This variation is caused by a number of factors, only one of which is a possible gain or loss of body fat. For example, every time you urinate 8 oz, you lose half a pound on the scale (one pint of water weights one pound), and every time you drink 8 oz of water you gain half a pound. With every bowel movement you can lose a half pound or more. Another factor is perspiration, through which much water can temporarily or permanently be lost. By becoming dehydrated after vigorous exercise, you may see a short-lived, lower-than-normal scale weight.

Let’s say that you weigh yourself before and after doing some very strenuous prolonged exercise. You might find that the exercise caused you to lose 3 lb. A fraction of an ounce of this weight loss might indeed be fat. The rest, however, is probably salt water lost through perspiration. You may even find that even though you later drink an ample quantity of water, 1 lb of the weight loss is permanent. Most of this 1 lb was very likely water bound by the salt, which was excreted but not replaced. That 1 lb eventually would have been lost without exercising just by restricting salt intake. The exercise merely accelerated the excretion of salt water. However, the exercise also burned a minute amount of fat. (More important, it helped to train the body to utilize fat for energy comfortably.)

How it is Possible to Lose a Pound of Body Fat and Not Weigh Less

1. Increase in Muscle. If your weight-loss program involves stepped-up exercise (and it definitely should), then your muscle mass is probably going to increase. This beneficial gain can offset your weight loss from fat reduction to the point where you are losing fat but gaining or maintaining weight.

2. Conversion of Fat to Water. Fat molecules consist primarily of long carbon chains containing hydrogen and carbon atoms in the ratio 2:1, respectively. When fat is burned in the body, its hydrogen and carbon atoms combine with oxygen to form H₂O (water) and CO₂ (carbon dioxide). These chemical formulas mean that two atoms of hydrogen (H₂) combine with one atom of oxygen (O) to form one molecule of water (H₂O) and that one atom of carbon (C) combines with two atoms of oxygen (O₂) to form one molecule of carbon dioxide (CO₂). Hydrogen, carbon, and oxygen atoms have relative masses of 1, 12, and 16, respectively. It follows from these facts that every pound of fat contains approximately 1/7 lb of hydrogen and 6/7 lb of carbon, and, when burned, every pound of fat combines with about 3.4 lb of oxygen to produce about 1.3 lb of water and 3.1 lb of carbon dioxide.

The carbon dioxide is quickly expelled by the body through respiration. But what happens to the water? The answer depends on a number of factors. First, every pound of body fat and every pound of body water contain about the same amount of salt. This salt is not necessarily all sodium chloride but salts containing other elements such as potassium. The reason for the presence of the salt is that human cells must be immersed in fluid that contains 0.9% salt (normal saline). Thus, when a pound of fat is burned, the resulting 1.3 lb of water will be left with slightly less salt than that characteristic of body fluid. Now, if excessive salt is ingested, the body may not be able to immediately eliminate the 1.3 lb of salt water resulting from burning 1 lb of fat. Thus, seeing the fat loss reflected in the scale reading may be delayed. You may even see a gain!

From the above discussion it is evident that, for successful weight loss, you should avoid all foods containing added salt. Given the fact that losing weight means having to eliminate salt, why compound the burden on the eliminative organs by consuming salt? Of course, there are many other reasons for eliminating added salt from the diet (see article on the effects of salt and condiments).

3. Water Retention in Hot Weather. During very hot weather, the body relies on perspiration for regulating its temperature. Because such regulation is so important, the body tends to retain extra water for this purpose. Thus, your weight might temporarily stay the same or even increase though you are losing fat.

It should be noted that water retention can be caused by other factors, some of which are serious and require medical intervention. One test for water retention is to press your finger into the flesh on your lower legs. The flesh should spring back immediately. A dent that remains for a while suggests water retention.

How Often Should You Weigh Yourself?

If you are going to take scale readings seriously, you must take into account all the factors that cause your weight to fluctuate. Otherwise, weigh yourself so infrequently that these fluctuations are less than your expected fat loss.

If your weight typically fluctuates by 2.5 lb during the course of a day, and your level of caloric restriction corresponds to a daily weight loss of 0.25 lb/day, then you should certainly not give any credence to scale readings taken more frequently than 2.5 ÷ 0.25 = 10 days. Even then, you may have lost 2.5 lb of fat but not see any loss on the scale. Or, you may not have lost any fat but read a loss or gain of 2.5 lb.

^*From Robert Chuckrow, The Intelligent Dieter’s Guide, Rising Mist Publications, Briarcliff Manor, NY, 1997, pp. 10–11.