Can you Become Obese by Eating Just an Extra Bite of Food per Day?

Jane Brody (veteran food columnist for the New York Times) recently reported, “According to researchers is easy to gain weight unwittingly from a very small imbalance in the number of calories consumed over calories used.” Brody continues, “Just 10 extra calories a day is all it takes to raise the body weight of the average person by 20-pounds in 30 years, the authors wrote.”
What do you think Ms. Brody meant in the preceding statement?