Unfortunately, this old saying doesn't make a lot of sense in the context of modern science.
These days artificial sweeteners are everywhere. Do they have any calories at all?
Trying to curb carbs? Processed sugar is more widespread than you think.
Many gorillas in zoos are overweight and dying of heart disease in their twenties and thirties when they could live to be twice that age.
You've just snacked on rice cakes. Why are you still hungry?
Teenagers are often a difficult bunch. With all those hormones flooding their bodies, they can be moody, unpredictable, and prone to making dubious choices.
What keeps seemingly defenseless grass from hungry grazers?
Have you ever heard that too much stress causes stomach ulcers?
Researchers have been studying moose for years and one thing they've found is while arthritis in moose is genetic, it's also triggered by the environment.
You exercise, eat right, and still have difficulty keeping the weight off. Could the problem be how your brain responds to dieting?