Recently Mayo Clinic posted an article describing how the metabolism affects weight loss, and summed it up by saying that food and exercise are the primary drivers of weight loss. The link to the complete article is below.
I agree with that statement, but only to a point. In his book, Why We Get Fat , Gary Taubes describes the metabolism of some people as more prone to accumulating and storing fat. Taubes continues in great detail to describe the history of the study of weight loss, and explains that some doctors have known for more than 100 years that some people gain weight more easily than others and have a harder time losing it.
As a former obese person who has kept her weight off for more than ten years, along with many friends who struggle with their weight, I wholeheartedly agree, as does the National Weight Control Registry, who claims that less than 10% maintain their weight loss .
Why then would an institution like the Mayo Clinic make the claim that weight loss is simply a matter of what you eat and how much you exercise? “You can help your metabolism – and your odds of weight-loss success – by changing your energy balance, or the balance between what you consume and what you burn off, through a healthy diet and regular physical activity.”
According to Dr. Robert Lustig, pediatric endocrinologist at the University of California Medical Center in San Francisco, and author of Fat Chance: Beating the Odds Against Sugar, Processed Food, Obesity, and Disease, “It's not simply a matter of calories in and calories out.” Certain foods, like sugar and refined carbohydrates trigger the release of the hormone, insulin, which is used to regulate sugar. As we now know, excess sugar converts to fat, and eating a diet without enough fiber exacerbates the insulin balance.
To prove this point, Dr. Lustig, along with his colleagues, conducted a study last year including 43 children who were put on a 9-day diet that restricted sugar, without reducing calories. Every measure of metabolic health improved: blood pressure, cholesterol, and blood glucose. What this showed, according to Dr. Lustig is that sugar is toxic because it's sugar, not because it's simply calories.
So yes, what we eat does affect our weight, but it is not as simple as pure energy balance. Some calories behave differently than others.
The entire Mayo Clinic article can be seen at: http://diet.mayoclinic.org/diet/move/what-is-metabolism?xid=nl_MayoClinicDiet_20161130 .