Fat Doesn’t Make You Fat

By , July 20, 2011

Eating Fat Does Not Make You Fat

Contrary to popular opinion, eating a diet rich in dietary fats does not make you fat. The prejudice against saturated dietary fat, as found in meat, diary, and some plant sources such as coconut, is based on extrapolations and incorrect conclusions.

It’s Not About Calories

One reason the “fat makes you fat” mantra has been repeated so often is that of the three macro-nutrients, fat contains the most calories per gram. Fat contains 9 calories per gram, while the other two, carbohydrates and protein, each contain about 4 calories per gram. Therefore, eat more grams of protein and carbs, and less of fat, and you reduce your caloric intake, and will lose weight.

Real life interferes with this fantasy. People don’t eat grams, they eat food. Arguments about whether a “calorie is a calorie” no matter its source don’t hold up to common sense. Instinctively we know that eating 125 teaspoons of table sugar is not as healthy as eating the 2500 calories in a well designed diet plan. And its more than just the nutritional value of foods; even if Big Food decides to infuse table sugar with vitamins, we know eating nothing but sugar isn’t good for us.

One of the “criticisms” of a low carb diet is that people spontaneously reduce the amount of calories they consume when they replace carbohydrates with fat and protein. This is seen as somehow cheating. Think about it, on every other diet the studies have to closely monitor the caloric intake of foods. But those same studies don’t put any calorie restrictions on the low carb diet group. They count only carbs. The low carb diet group in study after study loses more weight, faster, than any other diet group. The low fat advocates protest that the low carb diet group spontaneously eats less calories, and have therefore cheated.

Presumably, they want you to feel hunger, and be tempted to cheat on your diet, so that they can continue feeling superior to the weak willed fat people who simply can’t “move more and eat less.” What kind of diet is easier to adopt? One in which you are hungry, or one where you spontaneously reduce food intake?

There are numerous internet debates on whether a low carb diet has some magic “metabolic advantage”, or if the low carb diet is simply more satisfying, so people naturally eat less. A new study suggests that a high fat diet may actually cause the body to burn fat faster, as explained below.

Fat is Energy Dense

At 9 calories per gram, fat has more than twice the energy density of protein or carbohydrate. Rather than being a reason to reduce fat in the diet, this fact may be a clue to what studies have shown: a higher fat diet satisfies hunger faster than a high carbohydrate diet.

In the wild, given plenty of their natural food, all mammals assume a strikingly familiar profile. All well nourished wild cats appear about the same to other cats in their age group. Coyotes, feasting on rodents and other small animals, all look about the same. They don’t suffer from the obesity of their domestic canine cousins, who are fed unnatural diets by humans, or their brothers and sisters held in captivity. They have adapted to their natural diet, and even if they overeat on occasion, such as after a big kill, they don’t seem to gain weight.

Fat’s energy density may be the reason it is more satisfying, curbing hunger sooner than other foods. Mankind’s long evolutionary history of eating fat-rich food may have adapted us to be satisfied with a smaller amount of fat-rich food.

But hold on … science may have given us an answer as to why low carb diets are often said to have a “metabolic advantage”.

The Most Recent Study

The most recent study I have found is one in which six men, between the ages of 18 and 40, were tested to see how a low fat and a high fat diet affected lipolysis of their abdominal fat tissue. Lipolysis is the breakdown and use of fat as energy by the body. For overweight people, getting the body to “burn fat” is the usual goal.

There’s a reason studies like this one segment the subjects so specifically. Men with still-high levels of testosterone like this group may react differently than men over 50, who may have lower levels. Testosterone aids in lipolysis, which is one reason all those young guys at the gym seem to have such rapid progress. And its one reason that women in general and men over 50 have a harder time losing weight.

Only Six Particpants?

At first glance, having only six participants in a study may make it seem insignificant. But this study is different from the cohort studies that track a large population over a period of time and draw correlations from the data. Many of the dietary studies we see are prospective or cohort studies, or even meta-analysis of multiple cohort studies. The purpose of a cohort study is to identify trends, and develop a hypothesis that can be tested in a specific study like this one. So, in this case, having six participants in a direct study is actually more indicative of what really happens to individuals than a cohort study with hundreds or thousands of participants. In this type of study, unlike in the cohort study, specific measurements are taken at specific times of known people.

What Was Measured?

The study, Increased adipose tissue lipolysis after a 2-week high-fat diet in sedentary overweight/obese men, set out to determine if a high-fat diet affected the rate of “fat burning” in the six men. How do you measure the amount of body fat that has been burned? The most accurate way is to measure one of the by-products of lipolysis, glycerol, in the small amount of fluid that surrounds each cell (called the “interstitial fluid”). The more glycerol present, the more fat tissue has been broken down and used by the body as fuel.

The men adopted a high fat diet for two weeks, and had the interstitial glycerol measured. Then they ate their normal diets for 10 days. After this “washout period”, they ate a “well-balanced” diet with the same number of calories. A “well balanced diet” is usually code for a diet such as the USDA recommends, with high carbohydrate levels. After two weeks, the interstitial glycerol was measured.

Note that this method corrects for differences in calorie intake. Both diets were composed of the same number of calories, or were “isocaloric” in dietary study parlance.

Average interstitial glycerol concentrations (index of lipolysis) as determined using microdialysis were higher after the high-fat diet (210.8 ± 27.9 μmol/L) than after a well-balanced diet (175.6 ± 23.3 μmol/L; P = .026).

Not only did eating fat NOT make the men fatter, it actually increased the rate of fat burning by 20%.

Is This The Answer?

Hold on, grasshopper. This study does show that the fat cells release more fat on a “high fat” (and therefore lower carbohydrate) diet. But that’s all it measured. Is it possible that a high fat diet could lead to more storage of fat elsewhere? They don’t know:

These results demonstrate that healthy nonlean men who diet on the high-fat plan have a higher lipolytic rate in subcutaneous abdominal adipose tissue than when they diet on a well-balanced diet plan. This higher rate of lipolysis may result in a higher rate of fat mass loss on the high-fat diet; however, it remains to be determined if this higher lipolytic rate in men on the high-fat diet results in a more rapid net loss of triglyceride from the abdominal adipose depots, or if the higher lipolytic rate is counteracted by an increased rate of lipid storage.

I suspect that last sentence is being used to request more funds for another study!

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