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I lost weight by eating lots of bacon and cream. Here's a scientific explanation for why.

I recently gained 16 pounds of body fat and I felt terribly uncomfortable in my clothes. I wanted to slim down, so I decided to dramatically ramp up the fat in my diet. Every day for about a month, I slammed as much bacon or heavy whipping cream as I could stomach. I lost weight (about seven pounds). My cholesterol dropped 10 points. My afternoon drowsiness faded and, overall, I felt pretty good.

To be sure, there was a purpose to my bacon vacation. I wanted to test the limits of a growing divide between nutritionists on the benefits of fatty foods. Since the 1960s, conventional diet lore has demonized cream and fat as the culprit in America's obesity epidemic. Yet in recent years, a counter-revolution in the top rungs of the medical establishment, including the Harvard School of Public Health, have begged Americans to return to the naturally fatty diets of our ancient ancestors, who did not suffer from modern heart disease.

So, as Vox's eager health guinea pig, I decided to put it to the test in the most extreme way possible and get results just in time for the New Year's diet rush.

Greg, this sounds crazy. Do any doctors actually think this super-fat diet is *not* a terrible idea?

I spoke to a few experts and I got radically different opinions. Some doctors thought I was putting one foot in the grave; others thought I'd be just fine. Specifically, I asked medical experts what they thought would be the outcome of diet of mainly bacon, cream, and vegetables.

"This sounds like a very bad idea," Tufts University's Dariush Mozaffarian wrote to me. Likewise, Suzanne Steinbaum, a spokesperson for the generally anti-fat American Heart Association, told me that my cholesterol would surely increase — a lot. "LDL should go up," she predicted.

On the other side, University of California – San Francisco's Rob Lustig, an anti-sugar crusader, didn't see a problem. "The foods you list are saturated or monounsaturated fats. These are fine," he shrugged. Lustig told me he's only worried about the chemically altered franken-fats, such as trans fat, which have invaded snack and fast foods.

When I posed a question on HealthTap, a large online community of medical doctors, the immediate response from Scott Carollo, a cardiologist, was, "If you maintain this diet and seriously curb carbohydrates, you will likely see a notable weight loss."

The upshot is that gorging on a diet of bacon, cream, and vegetables is not universally condemned.

Ok, so what did you eat?

I tried to eat a diet where more than 70 percent of my calories came from fat. I regularly indulged in a wide variety of pure fats. I spoon-fed coconut oil, diced up fresh avocado, and poured on olive oil.

Even the foods I regularly ate got a fat supercharge: I coated steak in thick coat of grass-fed butter, salads were drowned in olive oil, and my morning green tea got a big dollop of coconut oil.

Yup, that's steak with butter on it. (Gregory Ferenstein)

Because I live in San Francisco, of course there's a startup at arm's length that's trying to solve my particular yuppie problem. A five-minute walk from my apartment in the Mission, I found an engineer, Evan Sims, who had quit his job for a high-fat yogurt startup. (Of course, I met him at a paleo food-themed brunch.) His cream-infused Greek yogurt has more than twice the calories of regular "full fat" yogurt — and I consumed a tub of it weekly.

But the real key to my diet was pork fat. A bespoke charcuterie, Boccalone, in San Francisco's historic Ferry Building imports Italian pigs. Boccalone slices the fattiest cuts of pork I've ever seen. I tried to consume at least a third of a pound of their delicious bacon per week.

I almost completely cut out carbs: very little fruit and no grains.

During the last week of my experiment, I kept losing weight, so I upped my fat count even higher. Every morning, I'd consume a fistful of fatty bacon and wash it down with at least a cup of cream.  My salads got smaller during this period to make room for all the pork goodness.

Were you consuming more calories?

No. Carbs awaken my appetite, and fat beds it back down to rest.

Breakfast ice cream (Gregory Ferenstein)

I purposely allowed myself to eat as much as I wanted two weeks prior and during the super-fat experiment. When I switched to fat, I ended up eating fewer calories. Fat is more satiating, per calorie, than carbs, and it curbed my otherwise ravenous appetite. I didn't even count calories; I just went with my hunger pangs.

I ended up learning a very important lesson: that carbs trick my body into consuming far more food than necessary.

The one time I gained weight over the course of my experiment is when I tested out a breakfast ice cream recipe, made with cream and the naturally no-calorie stevia leaf. My concoction was delicious: just these two ingredients form a kind of tart matcha-flavored ice-cream. However, compared to just drinking it from a carton, I consumed twice as much cream when it was frozen and sweetened with stevia.

This appears to be why diet soda is associated with weight gain. Sweeteners trigger hunger hormones, and all those diet soda fanatics end up consuming more calories.

What were the results?

I dropped about seven pounds and 1 percent of body fat over the month. Prior to the fat diet, I had gained 16 pounds eating whatever I wanted (which included lots of carbs). As soon as I cut carbs and loaded up on fat, the my widening waistline halted.

My cholesterol also dropped 10 points. I actually expected this result. For the last year, fat has always decreased my cholesterol. In a previous experiment, I tested a cult bodybuilding diet that involved several hours of dessert binging every night. The sugar caused a dangerous 31 percent spike in total cholesterol. Immediately afterwards I put myself on a steady diet of no-nitrate bacon  to help repair my arteries. Over the course a few months, thanks to a high-fat, low-carb protocol, my cholesterol returned to safe levels.

My cholesterol on various diets

(WellnessFX)

The same happened on last month's super-fat experiment. As soon as I slammed fat and ditched carbs, my cholesterol went down. It is also notable that my so-called "bad cholesterol," or LDL, maintained low levels. It normally fluctuates between 99 and 85. A sugary diet spiked it to 129.  After the super-fat diet, it was 97.

Wait, so why does everyone think fat is bad for people?

The roller coaster of recommendations started with a 1961 Time magazine cover story about Dr. Ancel Keys. Keys had made a name for himself as a World War II nutritionist and achieved medical superstardom for a study of cardiovascular disease around the world. Keys found an association between low-fat diet cultures and low rates of cardiovascular disease, and he concluded that fat was killing the rest of the population.

"The high frequency of coronary heart disease among American men, especially in middle age, is not found among many other populations, notably among Japanese in Japan and Bantu in South Africa," Keys wrote in a 1953 American Journal of Public Health article that would echo in hospitals around the country a decade later. "Evidence implicates the diet, and especially the fats in the diet, in these differences."

As tends to happen, a few interesting medical findings got overblown by a media frenzy, which eventually led to a mass public over-correction and a stampede away from fat and into straight into carbs.

"It was one big, happy, fat-free feeding frenzy — and a public health disaster," Barbara Moran wrote for the Harvard School of Public Health magazine.

How is this article different from all other articles?

This is part of a Vox series on better living through technology and science. I, your humble guinea pig, will subject myself to all sorts of experiments to discover what practical tips readers can apply to their lives immediately.

What makes this series different from traditional health writing is its emphasis on the techniques of "quantified self": the science of self-improvement. No single study can tell you, exactly, how a diet or exercise regimen will impact your particular body. When it comes to health, we're all individual snowflakes.

The stampede from steak, butter, and cream steered the masses into the hands of Big Carbohydrate, especially bread manufacturers. Instead of decreasing, heart disease and obesity ballooned.

"One problem with a generic lower fat diet is that it prompts most people to stop eating fats that are good for the heart along with those that are bad for it," a Harvard School of Public Health fact sheet on fats and cholesterol said.

After decades of criticism, the medical community settled on a compromise that some fats (monounsaturated), such as olive oil and avocado, do a body good.

The latest debate now focuses on whether any of the natural fats are harmful, as opposed to trans fats which are often chemically altered vegetable oils common in snack foods . A New York Times op-ed called "Butter is back" brought national attention to a new meta-analysis that could not find any credible link between saturated fat consumption and cardiovascular disease.

A 2014 article in the peer-reviewed British Medical Journal went a bit farther, in an article titled "Are some diets 'mass murder," criticizing the anti-fat craze for lack of scientific evidence.

"The successful attempt to reduce fat in the diet of Americans and others around the world has been a global, uncontrolled experiment, which like all experiments may well have led to bad outcomes," author Richard Smith argued. "It's surely time for better science and for humility among experts."

There are just too many factors that go into heart disease on a global scale; pin-pointing a few dietary components is suspect. We don't have good data. And hence we're now in scientific limbo where no one can give us a good idea if you should banish bacon or bathe in it.

What's the scientific explanation for what happened to you?

The traditional explanation for why fat was killing people was that it increased the proteins responsible for arterial plaque buildup, which can eventually weaken the heart. All foods have some fat in them, but for the same reason oil and water don't mix, the body can't readily absorb fat into the bloodstream.

In response to fat, the liver produces various sizes of particles, lipoproteins, to utilize fat's nutrient goodness. Low-density lipoproteins (LDL) are dubbed bad cholesterol because these little critters bind more easily to arterial walls.

Lustig argues that the medical literature misunderstood the link between saturated fat, sugar, and cardiovascular disease. His wonky explanation:

"If you are eating a lot of dietary fat, then the liver will package it as LDL, but the large buoyant (Type A) kind; the kind that does not promote [cardiovascular] disease," he wrote an in email. "But if you're eating a lot of sugar, then your liver is turning that into liver fat, which is packaged as VLDL, which raises your [triglyceride] level. Also, dietary sugar will make your liver insulin-resistant; then your liver makes small dense (Type B) LDL instead, which does promote cardiovascular disease."

This is one explanation for why saturated fat lowered my cholesterol, but sugar increased it.

But why does research show that fat increases heart disease in some populations?

Two reasons:

The original fat studies were observational, not experimental. When looking at a mass of people, its nearly impossible to distinguish all the different types of eating habits. If people who eat fatty foods also eat more transfats and exercise less, we'd see a correlation between high fat and heart disease. This is why more granular follow-up studies failed to find the same association, once researches started looking at the link in greater detail.

Second, genetics. "One of the problems with dietary recommendations is that it does not take into consideration the individual," said the American Heart Association's Suzanne Steinberg. "Everyone metabolizes food differently.  For those people who have a family history of heart disease at a young age, very often they can't metabolize fats."

Steinberg suspected that I didn't have a genetic abnormality that causes people to metabolize fat poorly. But I checked my 23andMe and, indeed, I do have the allele that she said causes the abnormality. It's still possible that my unique genetic code is a factor in why I can bathe in fat, but, for the moment, I have no clue where to look.

Are there benefits to eating fat?

Fat is an essential ingredient for absorbing nutrients. An experimental study from Iowa State University found that blood samples of students who ate fat-free salads were devoid of many of the healthy vitamins they were consuming.

"A substantially greater absorption of carotenoids was observed when salads were consumed with full-fat than with reduced-fat salad dressing," the study concluded.

And fat just isn't an empty vitamin taxi. Its's often loaded with vitamins E, K2, and D, plus a whole host of other nutrients.

But don't you feel awful eating all that fat?

Actually, I felt great, especially after polishing off a few rows of bacon. Fat is a slow-burning energy source, which I find gets me through the afternoon sleepiness. One military study found that high-fat meals improved pilot simulator performance more than either a high-carb or high-protein meal.

To test the effects of a super high-fat meal, I ate a home brewed zero-sugar ice cream and measured my mental performance on a series of reaction time tests on the cognitive testing websites quantified-mind.com and humanbenchmark.com.

In previous experiments, I found that lunch gives me the yawns and my reaction time drops 13 percent. However, on the super-fat diet, ice cream boosted performance about 28 percent. These tests lend some nice quantitative evidence that eating fat did make me feel a-OK.

So, when you're on a normal diet, how do you incorporate fat?

I add fat to my diet in in two strategic ways

1) If I want to slim down, I enter ketosis, eating fewer than 50 grams of carbohydrates per day. I find that this helps me drop fat for about two weeks. Afterwards, ketosis stops working.

2) On my normal diet, I never avoid fat. I eat marbled slices of steak, pour olive oil on salads, and never eat anything that says "low fat." I try to eat food as close to its natural state as possible, and that often means a lot of delicious, juicy fat.

When I want to lose weight, I pack on the bacon. Even if I just want to remain healthy, I make sure to love me some butter.

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