Calories Lie.  No, Really, They Do.

How many of us have heard time and time again that if we simply count calories and stay active, we will be able to lose weight/gain weight/keep our weight stable?  While making sure that we are eating appropriately for our goals and activity levels is certainly important, there are a lot of different ways in which calories do not give us an accurate understanding of what our bodies really need, both on the “calories in” and “calories out” side of the equation.  Here are just a few common misconceptions:


  1. Food labels and databases are based on averages.  What you are eating may differ substantially from those averages.  Just type in any food on any common dieting application and you’ll see a wide range of calories for the exact same food.  Moreover, when preparing food labels, companies may use any one of five different methods to estimate calories, so the FDA permits inaccuracies of up to twenty percent.  In other words, 150 calories could really be anywhere from 130 to 180 calories!
  2. We don’t absorb all of the calories we consume.  Absorption rates vary widely from individual to individual and among various foods that we eat.  For example, people typically absorb fewer calories from nuts and seeds and more calories from fiber rich foods.
  3. The manner in which we prepare a food changes the number of calories available for absorption.  Cooking an egg or a potato, for example, nearly doubles the number of calories that can be absorbed.  Chopping or blending a food also increases the number of calories that can be absorbed.
  4. Different types of gut bacteria change the calories we absorb by up to 150 calories!
  5. Eyeballing portion sizes rarely works.  People tend to use incorrect portion sizes approximately two-thirds of the time, so unless you are weighing and measuring all of your food, you likely are eating more than you think.


  1. Have you ever looked up how many calories you just burned by doing a particular exercise?  Well, almost all of those calorie expenditure tools are inaccurate because most use testing methodologies that large margins of error.  Fitness trackers are no better, demonstrating error rates of up to thirty percent.  Even the best out there have error rates of ten percent or more under most circumstances.
  2. Just as the number of calories absorbed varies tremendously from individual to individual, the number of calories burned by an individual is unique and variable.  Genetic, epigenetic, hormonal, and environmental factors all play a big role in determining how many calories your body burns.  For example, sleep deprivation for a single night may decrease calories burned by anywhere from five to twenty percent, and the calories burned by the typical woman may vary by over a hundred calories depending on where she is in her menstrual cycle.  It is not uncommon for an individual’s metabolic rate to vary on a daily basis by as much as 100 calories.
  3. Different people’s metabolisms adapt differently to caloric surpluses or deficits.  Sometimes, the math lies.  In one study, researchers had subjects eat an additional 1,000 calories per day over their maintenance needs for a period of eight weeks.  Weight gain ranged from less than one pound to nearly ten pounds.  Doing the strict math, all of the participants should have gained much more.  Side note:  This is a major reason why when someone tries to gain weight to increase muscle mass on purpose, it actually takes a lot more effort than you would think!
  4. Digesting some macronutrients burns more calories than others.  Your body will use more than twenty percent of the calories it absorbs from eating protein to digest it.  By contrast, your body uses very little energy to digest fats.
  5. Your weight history influences your caloric needs.  If you have lost significant amounts of weight in the past, your body adapts to that weight loss and makes you more efficient so that you burn fewer calories to do the same work.


Well, the answer is that most people don’t have to in order to be successful in adjusting their diet to a maintenance level or for weight loss purposes.  (Athletes competing at a high level or who have set particular goals for themselves often are the exception).  However, if you do choose to track calories, the important thing to remember is that what your body needs is unique to you.  Calories should give you data on which you can make good decisions about your nutritional needs, but you should not rely on calorie estimates to determine what YOU should be eating.  Similarly, you should not be relying on your FitBit to tell you whether you “can” have dessert or a piece of pizza.  Success with nutrition for most lies in creating solid habits that are repeated day in and day out.

Amy Mariani

Nutrition Coach, Mountain Strength Crossfit

Owner, Fit & Fabulous LLC

To book a nutrition consultaion with Amy Click Here