Eat fat to lose fat – wait, what? Nutrition experts and public health officials have been telling us for decades to eat less fat to lose weight. But it turns out a high-fat diet can actually help you lose weight, gain energy and fight obesity-associated conditions such as diabetes. Why did the experts lead us astray for so long? In short, weak science is to blame.
The origin of low-fat diet recommendations can be traced back to Sept. 24, 1955 – the day President Dwight Eisenhower suffered a heart attack. That event raised public awareness about the dangers of heart disease and gave one outspoken scientist, Ancel Keys, a platform to promote his research findings showing a correlation between heart disease and dietary fat consumption. The problem was the findings were merely correlative and didn’t show that consuming a high-fat diet causes heart disease. Despite the lack of hard scientific evidence, the American Heart Association released dietary recommendations in 1961 suggesting people reduce intake of total fat, saturated fat and cholesterol and increase intake of polyunsaturated fat.
These new recommendations prompted the food industry to develop a wide array of fat-free and low-fat foods. But what replaces fat when it is removed from foods? A large portion is replaced by sugar and the remainder by thickeners and emulsifiers. Health-conscious Americans jumped on the low-fat bandwagon and replaced butter with margarine, whole eggs with egg whites, and other common foods with their low-fat counterparts in an effort to promote better health. And after several decades, what are the results? A huge increase in obesity and diabetes, not only in adults but also in children.
Experts such as Robert Lustig, a pediatric endocrinologist at the University of California, San Francisco, and Gary Taubes, co-founder of the nonprofit Nutrition Science Initiative, say sugar is to blame.
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For thousands of years, most sugar was consumed in the form of fruit that was only available in the summer months. Our bodies are not designed to process all the refined sugar most of us consume today – on average about 150 grams of sugar daily, or 15 times the amount consumed prior to the Industrial Revolution.
How does all of this sugar end up in our diet? Obvious sources include sodas, pastries and candies as well as sugar from insidious sources such as sauces, dressings and sugar bombs parading as health foods – flavored yogurts, granola bars and fruit juices. The American Heart Association now recommends limiting added sugar intake to 100 calories a day for women and 150 calories a day for men – a more conservative recommendation than the 2015-2020 Dietary Guidelines for Americans, which advises limiting added sugars to 10 percent of caloric intake.
Why is sugar so detrimental? Excess sugar in the body attaches to proteins, lipids and DNA, forming advanced glycation end products that can impair protein function, damage cellular membranes and lead to genetic instability. Sugar also causes the pancreas to release the hormone insulin, which binds to receptors on the cell surface, allowing glucose to enter the cell and lowering blood sugar levels.
Many people consuming high-sugar diets become insulin-resistant, meaning cells in the body no longer respond to insulin. This prevents glucose from entering cells, and blood sugar levels remain high. A vicious cycle starts, where the pancreas pumps out more insulin in a futile effort to reduce blood sugar levels while the cells starved of fuel needed for energy production send out signals for the body to eat more. All of this results in you feeling tired and hungry. Insulin also signals to the body to store excess sugar as fat, so when insulin is present, the body will not break down stored body fat.
Compared to sugar, fat is burned more efficiently by the energy-producing component of the cell known as the mitochondria. This means you get more energy from your food and fewer of the negative by-products known as reactive oxygen species. In excess, these free radicals can wreak havoc on your body – similar to the way advanced glycation end products do.
It’s not just that sugar is bad for you, but dietary fat is actually vital for survival. Fat is needed for production of cell membranes and hormones and aids in the absorption of fat-soluble vitamins and beneficial plant metabolites such as polyphenols. However, not all fats are created equal. Contrary to popular belief, saturated fats are good for you and many polyunsaturated oils may actually be harmful.
Polyunsaturated oils from corn, safflower and soybean contain lots of omega-6 fatty acids, which are precursors to inflammatory compounds known as eicosanoids. Saturated fats, like those found in grass-fed butter and coconut oil, contain anti-inflammatory compounds. Other sources of healthy fats include avocados, nuts, seeds, egg yolks and grass-fed beef. And no worries if you can’t give up sweets entirely: Natural sugar substitutes such as stevia, xylitol and monkfruit make for suitable replacements.
If you want to lose weight, increase energy levels, reduce inflammation and balance your hormones, you could investigate whether a high-fat, low-carbohydrate diet is right for you. Two recently published books, one from Dave Asprey, “Head Strong,” and another by Joseph Mercola, “Fat for Fuel,” are great resources.
Dorothy Kieffer is a postdoctoral scholar at UC Davis researching the effects of diet on the genetic disorder Wilson disease.