Serving Size and Calorie Counting

When you want to lose body fat, the only way to do it is to burn more calories than you consume.  If you burn approximately 3500 calories more than you eat, your body will metabolize about 1 pound of fat to make up the difference.  Now this has some interesting implications...  Can you lose weight eating only Krispy Kreme donuts?  Well, yes.  You just need to eat less calories worth than you consume.  Of course, an all-Krispy-Kreme diet would almost certainly lead to other nutritional complications.  You would also probably be hungry most of the time because eating few enough donuts to lose weight would probably not be very satisfying.  But it could be done.

If you are keeping track of you calorie intake, it is important to know what your actual calorie count is.  Small errors add up over time.  An extra 10 calories a day, which is less than one teaspoon of sugar, adds up to 3650 calories over a year; that's more than a pound of fat!  Fortunately, there are standard nutrition facts labels on virtually all packaged foods sold in the United States, like this one on tortilla chips:

So, according to this label, the serving size is 28 grams, which is 140 calories.  The FDA has rounding rules that allow manufacturers to round to the nearest 10 calorie increment for values >50 calories, so that means the real value is somewhere between 135.0 and 144.9 calories per 28 gram serving.  Also, most people don't have or regularly use a food scale, so the label often helpfully provides a translation of the serving size into pieces.  Here that is "About 13 chips."  So when I was making nachos the other day I wondered "how close is 'about?'"  The answer was, not too close:

Counting out 13 of the most uniform chips I could find onto a scale (yes, I zeroed out the paper plate), I measured 34.7g, which is 6.7g, or 24% more than the 28g serving size.  That means that if I count out 13 chips and think I'm eating 140 calories, I would really be getting closer to 174 calories.  To get the 28g serving size, I should really eat about 10.5 chips.

To be really precise, I should note that the primary measure for the serving size is given as 1 ounce, which is really closer to 28.35 grams.  But that .35 grams is an error of only 1.25%, which is dwarfed by the 24% error above.  There is also some normal chip-to-chip variation, which I didn't measure.  And often a "chip" is actually broken and missing part.  But ultimately, if you want to confirm serving size, the best way to do it is by weighing your food.

Do you ever keep track of your calorie intake?  Leave a comment below!