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Knowing exactly how much we are really eating can be difficult unless we have scales at the ready when we are out and about. To assist people in monitoring their intake, researchers from the University of Sydney have developed a novel, easy to use method for people to estimate food portion sizes using only their hands.
How does the new method work?
Given that many foods conform to certain shape, the width of fingers is used as a ‘ruler’ to measure the dimensions of foods, and volume formulas are then used to calculate the weight. For example, the dimensions of a piece of lasagne may be 7 by 5 by 4 fingers, calculated by the volume formula for a box would give the weight of the portion.
For foods that are not so geometrically shaped for example a serve or mash potato or rice, fists and fingers tips can be used to estimate the portion size.
What did they find?
Sixty-seven participants took part in the study where they were presented with various pre-weighed foods and drinks and asked to estimate the portion size using the hand method and also using household measures. For geometrically shaped foods and liquids assessed with the finger width method, 80% were within 25% of the true weight of the food, compared to only 29% of those estimated using the household method being within 25% of the true weight.
Geometrically shaped foods such as a slice of pizza or cake tended to be more accurately estimated than those that didn’t conform to a geometric shape such as a chicken breast, fish fillet or beef steak. For these three foods, estimations with both the finger width method and household method were all above 50% of the true weight.
Using the fist method for 8 different amorphous foods such as mashed potato, muffins and rice, no food was estimated to within 10% of its true weight and only one food was estimated to within 25% of it true weight. Furthermore, for spreads estimated using the fingertip method all were significantly different from their true weight.
What are the advantages?
Currently, the most accurate method for measuring portion sizes is to weigh your food, however unless you want to carry around scales this method is fairly impractical. For this reason, those monitoring their portion sizes tend to rely on the art of estimation using either common household measures or by describing the size of the portion i.e. small, medium, large. Understandably this technique is rort with error and inaccuracies. This new hand method therefore has its advantages in that it is portable, inexpensive and universal. For foods that closely resemble a geometric shape the method also provides reasonably accurate estimations. Furthermore, it has potential to be easily incorporated into electronic food records useful in research, clinical and educational settings.
What are the limitations?
The finger width method is not a 100% accurate form of measurement and therefore more research is required to fine tune it, particularly for foods that do not conform to a geometric shape. For this method to be implemented more widely integration into phone apps will be the best utilisation so as calculations are automatic.
It is an easy to use method that is available to people anywhere and at any time. The method will assist in improving the accuracy of food and drink portion estimations and therefore prove useful for those monitoring their intake and for dietitians in providing more tailored nutrition advice and recommendations to their clients.
Gibson A, Hsu M, Rangan A, Seimon R, Lee C, Das A et al. Accuracy of hands v. household measures as portion size estimation aids. Journal of Nutritional Science. 2016; 5(29). Available from: https://www.researchgate.net/publication/305210921_Accuracy_of_hands_v_household_measures_as_portion_size_estimation_aids