Changing Views on Fats

There’s a six decade-old scientific legend that just refuses to die, and researchers such as myself would love to set the record straight. I’m sure you’ve heard it before, probably even from your doctor: High-fat diets are bad for you and saturated fatty acids cause heart problems and make you fat.

A growing body of solid scientific research, however, shows otherwise.

So how did saturated fat earn such a negative reputation? Let me take you back to the early 1900s.

Back then, people used butter, lard, and beef tallow almost exclusively in cooking and baking. (Of note, heart disease was relatively rare, too.) But then two things happened.

First, women began dieting (by counting calories) to stay thin. Since a gram of fat has more calories than a gram of protein or carbohydrate (9 vs. 4), they naturally chose to eliminate the higher-calorie macronutrient in favor of lower-calorie ones.

In addition, it came to light that mechanically hulling and pressing seeds to make vegetable oil was much cheaper and faster than raising cattle to milk for butter or slaughter for their lard or tallow. The food manufacturing industry quickly entered the picture to patent the creation of hydrogenated vegetable oils and market them as the healthier, more sanitary choice for cooking and baking.

The reduction of dietary fat for slimmer waistlines was pretty commonplace by mid-century, around the time that researchers began searching for answers on a once-rare condition starting to affect more and more people—heart disease.

Ancel Keys was one of the most well-known researchers to introduce the idea that saturated fat may contribute to the development of heart disease. His “Seven Countries Study”—a 20-year trial, starting in the late 1950s, that followed more than 10,000 men in Italy, the Greek Isles, Yugoslavia, Netherlands, Finland, Japan, and the US—was one of the first major studies to link saturated fat consumption with heart disease. He found that countries with the greatest consumption of saturated fat had the highest rates of heart disease.

Even though the study had some serious flaws (for one, it showed a correlation between saturated fat and heart disease, it did not prove cause and effect), the damage was done. The medical establishment adopted the notion that fats are bad for the heart and should be avoided.

The “low-fat for heart health” craze was in full swing by the mid-1980s, when a study published in the journal Circulation concluded that obesity was an independent risk factor for cardiovascular disease. Not only did this finding lend further fuel to the “fat is bad for your heart” fire, it also put back into the spotlight the dangers of obesity—and that high-calorie dietary fat may make your waistline fat.

By the 1990s, you couldn’t enter a grocery store without seeing the shelves dominated by low-fat or nonfat food options—from skim milk and nonfat yogurt to low-fat processed snack foods.

Interestingly, though, America was not getting skinnier. In fact, people were heavier than ever and heart disease was more prevalent than ever.

Why? Well, the biggest issue with low-fat diets is that they tend to be high in carbohydrates. Your body converts carbs to sugar. This blood sugar spike initiates an insulin response, which is designed to bring down circulating sugar levels. Additionally, excess sugars get converted into a fat called triglycerides, which get stored as body fat.

The problem is, with carb-heavy diets, blood sugar never has a chance to drop to normal levels. The never-ending stream of insulin triggers a constant state of fat storage and damages the insulin signaling system. Eventually, this relentless sequence of events leads to obesity, insulin resistance, and diabetes in large numbers of people.

Moreover, low-fat foods are almost always high in sugar. Fat adds flavor. Strip the fat, you take away the flavor. (Simply compare the rich flavor of whole milk to watered-down skim milk, and you’ll understand what I’m talking about!) To add flavor back into low-fat or nonfat foods, manufacturers typically add sugar. And you already know what an inflammation-causing health destroyer sugar is on so many levels.

Conflicting Research Revealed

Finally, the medical community was starting to consider that maybe reduction of fat was part of the problem—not the solution.

In one meta-analysis of randomized trials, researchers found that, in the short term, low-fat diets resulted in weight loss. Long term, however, is a different story. They wrote, “in trials lasting one year or longer, fat consumption within the range of 18-40% of energy has consistently had little, if any, effect on body fatness. Moreover, within the United States, a substantial decline in the percentage of energy from fat during the last two decades has corresponded with a massive increase in obesity, and similar trends are occurring in other affluent countries. Diets high in fat do not account for the high prevalence of excess body fat in Western countries; reductions in the percentage of energy from fat will have no important benefits and could further exacerbate this problem. The emphasis on total fat reduction has been a serious distraction in efforts to control obesity and improve health in general.”

Other research started to cast doubts on the link between saturated fat and heart disease.

A 2010 meta-analysis of 21 studies (and more than 347,000 people) found “no significant evidence for concluding that dietary saturated fat is associated with increased risk of coronary heart disease or cardiovascular disease.”

And an even more recent 2014 meta-analysis of 80 studies (involving more than 530,000 people), including 27 randomized, controlled trials, concluded that “current evidence does not clearly support cardiovascular guidelines that encourage high consumption of polyunsaturated fatty acids and low consumption of total saturated fats.”

The main reason saturated fat is so vilified is that it can increase low-density lipoprotein (LDL) cholesterol. (It also happens to increase beneficial high-density lipoprotein (HDL) cholesterol.) LDL cholesterol has been linked to higher heart disease and heart attack risk. However, the subtype of LDL that saturated fat raises—LDL pattern A—is actually relatively harmless.

LDL pattern B—the smaller, denser form of LDL—is much more dangerous. It causes inflammation, which sets off a chain of events that eventually leads to heart disease and countless other inflammation-related issues. LDL pattern B levels are not elevated by saturated fats. They’re raised by high-sugar, high-carbohydrate diets.

Finally, I think it’s important to note that saturated fat actually plays some pretty critical roles in the body. You can’t completely live without it. It is a component of all cells, and also helps the body digest and use proteins, omega-3 fatty acids, and other fat-soluble vitamins.

I hope this information helps you understand that the scientific evidence now reveals that saturated fat is not as harmful as it has been made out to be over the past several decades. If you’re still avoiding that juicy steak or glass of whole milk for fear that it may give you a heart attack or increase your girth, it’s ok to indulge a little. Don’t go overboard…still practice moderation. But there’s simply not any scientific proof that you should avoid it altogether.