You're Probably Eating More Than You Think

According to studies, we underestimate how many calories we eat by 20%-40%! (1)

To make it worse, the more calories in the meal, the fewer calories we tell ourselves it contains! We underestimate the calories in small meals by 10% calorie and large meals by up to 40%! 

Another diet blunder is that if a product is labelled ‘lower in fat’, we consume 50% more than people using the full fat alternative. Many of us believe that because a food is described as healthy it must, by default, contain fewer calories.

Scientists, physicians, and counsellors have often blamed overweight people as trying to fool others, and themselves, about how much they are eating. But the studies say otherwise! According to (2) overweight people seemed to be pretty accurate at estimating the calorie content majority of the time with all sorts of different foods. They go on to say that the overweight people they studied were no less accurate than the skinniest people in the lab. These results were the opposite of what all the classic scientific studies report. So what was happening?

It all came down to psychophysics. Psycho what now?! This term means that we consistently underestimate things as they get bigger.  This is consistent is all areas such as weight, height, brightness, loudness, sweetness etc.

For example, we will be fairly accurate at estimating the weight of a 1kg rock but will grossly underestimate the weight of an 40kg rock. Scientists believe this is the key to the calorie mystery (3).

In other words, this mystery may not be in the size of the people, but in the size of the meal. Which is why it is a common myth that larger people would overestimate their calories, but the actual reason might come down to the fact that their meal is larger in general than the smaller person.  As states “It's meal-size, not people-size.”

I thought this was very interesting from a study done by… 

“First, we recruited 150 people who were either normal weight or obese.  We then bought a dozen different meals of all different types – small sandwiches, huge sandwiches with chips, small chicken dinners, large chicken dinners with fries and a 650ml Coke, and so on.  We asked each person to estimate the number of calories in each of the 12 meals.  The results were alike, regardless of a person’s weight.  The smaller the meal, the more accurate people are at estimating its calorie-level.  The larger and larger the meal, the fewer and fewer calories they thought it contained. Everyone estimated a huge 2000 calorie meals as only having 1200 calories or so. There were no differences in the estimates of the skinniest people or of the largest people.”

Read more: Your Guide To Eating Out

What does that mean for me?

Firstly, let’s all not feel bad! Even dietary experts often get it wrong. According to an article by FitDay, a study of 200 nutritionists, stated by WebMD, revealed that many were unable to guess the number of calories in restaurant meals, with some estimating just 50 percent of the actual count. Phew, we are all normal!

My advice would be to always OVER estimate when eating out. A lot of chefs add secret calories to food via hidden oils and fats etc. So if you think a meal is 500 calories, add another 150-200 calories! That way you have your bases covered JUST incase. 


  1. This gap in our calorie estimation and the exaggerated gap among obese peole has been widely reported by top scholars over the past 20 years.  The classic studies include: David Lansky and Kelly D. Brownell, "Estimates of food quantity and calories: errors in self-report among obese patients," American Journal of Clinical Nutrition(1982), 35:4, 727-32.  Steven W. Lichtman, Krystyna Pisarska, Ellen R. Berman, Michele Pestone, H. Dowling, E. Offenbacher, H. Weisel, S. Heshka, D.E. Matthews, S.B. Heymsfield, "Discrepancy Between Self-reported and Actual Caloric Intake and Exercise in Obese Subjects," New England Journal of Medicine(1992), 327:27, 1893-1898.  M. Barbara E. Livingstone and Alison E. Black, "Markers of the Validity of Reported Energy Intake," Journal of Nutrition(2003), 133:3, 895S-920S.  Janet A. Tooze, Amy F. Subar, Frances E. Thompson, Richard Troiano, Arthur Schatzkin, and Victor Kipnis, "Psychosocial Predictors of Energy Underreporting in a Large Doubly Labeled Water Study," The American Journal of Clinical Nutrition(2004),79:5, 795-804. 


  2. Pierre Chandon and Brian Wansink, “Obesity and the Calorie Underestimation Bias: A Psychophysical Model of Fast-food Meal Size Estimation,” Journal of Marketing Research, (2006). 

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