To Lose and Keep Off Weight, Turn Off Your Body's 'Fat Switch'

Most people don't think about fat insects or hibernating animals when they talk about the cause of obesity, so it's refreshing to see a book that tackles obesity as a normal process that all animals have learned.
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Most people don't think about fat insects or hibernating animals when they talk about the cause of obesity, so it's refreshing to see a book that tackles obesity as a normal process that all animals have learned.

In his new book The Fat Switch, Richard J. Johnson, a professor of medicine and head of the division of Renal Diseases and Hypertension at the University of Colorado-Denver, argues that obesity is a process animals have used to protect themselves during periods of food shortage, and that they have learned to "flip" a switch when they want to gain weight. The switch occurs in the energy factories of the body (mitochondria) and results in the desire to eat more than is needed and to reduce energy output, thus allowing the maximal conversion of food into fat.

The usual argument is that people gain weight because they eat too much and exercise too little. They blame large portions of food, supersize drinks, TV, the Internet and video games. But Johnson says the real reason people are getting fat is that they have inadvertently activated the "fat switch." In other words, we are eating more not because we are given bigger servings of food, but because we demand bigger servings, and we are exercising less not because we are watching more TV, but we are watching more TV because we have less energy.

So what flips the fat switch? In a word: sugar. More precisely, says Johnson, it is the excessive uric acid that results from excessive sugar consumption. For years, we have heard messages about watching our saturated fat intake. But in reality, sugar is the real cause of our expanding waistlines.

"Fat is the fuel, but sugar, and in particular, fructose, is the fire," says Johnson. "Foods rich in fructose can activate the fat switch -- resulting in loss of appetite control and a reduction in energy."

The major sources of fructose are table sugar (sucrose, which contains glucose and fructose), and cheap, ubiquitous high-fructose corn syrup (HFCS), which is often added to foods to enhance taste. Fructose can also be generated from carbohydrate-heavy diets. "In the big picture," said Johnson in an interview, "it's sugar and high-fructose corn syrup driving this obesity epidemic. But you can make sugar from carbohydrates."

Although sugar is the major culprit, Johnson also argues that humans are particularly sensitive to the effects of sugar. He says that millions of years ago, our ancestors dwelled in rainforests and subsisted on fructose from natural fruits. But global cooling led to disappearing rainforests and famine during the colder months when fruits were unavailable. This led to a genetic mutation that resulted in a greater uric acid response to fructose. "This mutation was life-saving," Johnson explained, "as it allowed animals to convert fat much more effectively from fruit."

All was well for millions of years -- until the discovery of sugar cane and, with it, plentiful fructose. Today, one can drink huge amounts in one supergulp soft drink. And we have become super-effective at converting the fructose to fat. "So what was life-saving in the past," says Johnson, "is driving obesity today -- a great irony."

Making matters worse, the more sugar we eat, the more uric acid our bodies produce, which increases our liver and intestines' ability to absorb sugar. "Obese people absorb fructose more easily," says Johnson, "whereas skinny people don't absorb it very well."

If nothing changes, Johnson told me, it becomes "like a snowball rolling down the hill." He explained, "The more sugar you eat, the more uric acid you make. And the more uric acid, the more metabolism of fructose that occurs."

Once the snowball has increased in size and speed, it's harder to stop it. "In the early phase of obesity," says Johnson, "if you cut out the foods you recover your weight. But over time, it looks like you lose [the energy-producing mitochondria] and can't recover them. It seems you reset yourself to a higher weight."

The net effect: an increase in fat accumulation, insulin resistance (Type 2 diabetes), higher blood pressure and triglycerides, and stimulation of low-grade inflammation that activates the immune system. Coronary artery disease, strokes, aortic aneurysms and congestive heart failure are just some of the complications linked to sugar-fueled obesity.

If this all seems bleak and hopeless, take heart. Johnson suggests in The Fat Switch that keeping the switch off -- which is essential for good health -- depends on following a few general principles.

Of course, reducing your intake of added sugars is key. Johnson recommends no more than four to five teaspoons per day. "The first step is to eliminate soft drinks and fruit punches with added sugars," he writes, "as the effects of fructose relate to the concentration that the liver is exposed to, and this relates not only to the amount ingested but also the rate. However, natural fruits are OK as they have a lot of good ingredients like vitamin C and antioxidants that block the effects of sugar."

Another important step is to reduce carbohydrates -- but only at certain times of the day. "I think most people would like to maintain a normal balance of only 25 to 30 percent carbohydrates, at least 15 percent protein and the rest fat," says Johnson. "However, the key way to lose weight is to simply restrict the carbohydrates for two of the three meals of the day. This allows the body to burn fat for much of the day." At least 30 minutes of exercise and at least eight hours of sleep every day have additional health benefits.

Johnson recommends limiting purine-rich beer because it increases uric acid production. Interestingly, both regular beer and nonalcoholic beer are problems, because the purines are from the brewer's yeast, not from the alcohol. Do, however, drink milk and eat cheese, as they are associated with reduced risk for obesity, diabetes and gout. Coffee drinking also appears to reduce the risk of developing diabetes, and is likewise associated with lower uric acid levels.

Eating a quarter of a big bar of 70 percent dark chocolate per day appears to replenish the cell mitochondria needed to control fat production. In fact Johnson says research is showing that the flavinol in dark chocolate, epicatechin, can actually block many of the effects of fructose -- in studies of rats, so far. Even more promising, he writes, "Epicatechin appears to be one of the most potent stimuli to grow mitochondria that has ever been discovered. It may improve muscle mass and exercise performance of aging mice. And it has been shown to increase mitochondrial function in human patients with heart failure."

With promising discoveries like these, Johnson told me, "It's really an exciting time." Most exciting of all, as he writes in The Fat Switch, "For those of you who wish to see the day when obesity can be cured, I believe it will not be long."

The Fat Switch is available in hardcover at and Kindle e-book at

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