We are all survivors of food scarcity as our ancestors lived through multiple periods of famine. We survive by storing body fat.

Richard J. Johnson, MD, of the University of Colorado, is a leading physician and scientist who studies fat storage as the “survival switch” to protect us from starvation. He shares his findings in his new book Nature Wants Us to Be Fat: The Surprising Science Behind Why We Gain Weight and How We Can Prevent-and Reverse-It.

Much of the book discusses sugar, which we all know leads to fat storage. However, Johnson further explains that the sugar which most leads to fat storage is fructose (versus glucose) as noted in a recent discovery. While the body uses glucose for energy, fructose goes to the liver to trigger making fat for storage. Table sugar is called sucrose, consisting of glucose and fructose in equal amounts. High fructose corn syrup (HFCS), the most common sweetener used today, is about 65 percent fructose and 35 percent glucose. This is why HFCS, used in sodas, salad dressings and many other processed foods, leads to more fat storage causing today’s epidemic of fatty liver, overweight and obesity.

Starchy foods like potatoes and rice have a carbohydrate called glycogen that is chains of glucose molecules and no fructose. These foods are called “safe starches” and do not readily lead to more body fat.

As Johnson discusses in this educational book, fruits are high in fructose and among the most fattening of foods. Bears consume tens of thousands of berries to acquire enough fat to survive a winter of hibernation. The author studies many mammals besides humans and describes this biological survival switch among the animal kingdom.

Another part of the survival switch is to rapidly accumulate fat once it is lost. A cruel part of having excess body fat is that the body will adjust its metabolism to accumulate more fat than in a person who has been lean.

Losing weight requires burning body fat through low carbohydrate nutrition, especially low fructose. To remain at a healthy weight, a person needs to follow a low carbohydrate nutrition plan – as a lifestyle – including limiting fruit to no more than two to three servings daily and consuming fruits that are less glycemic such as berries, kiwi and avocadoes. Periods of fasting, or time restricted eating, of more than 12 hours daily also helps in burning fat for energy and avoiding a trigger of the fat storage survival switch.

Nature Wants Us to Be Fat is a great addition to understanding the science behind overweight and obesity. The language is easy for anyone to understand. I no longer look at fruit in the same way and am conscious of limiting my intake every day.

Dr. Scherger is founder of Restore Health in Indian Wells, a clinic dedicated to weight loss and reversing disease. For more information, visit www.restorehealth.me or call (760) 898.9663.