Investigative journalist Nina Teicholz, author of The Big Fat Surprise, explains how several shocking discoveries led her to radically change her family's diet.

By Nina Teicholz

Seven years ago. That was the first time I bought a piece of red meat—a flank steak. It sat, accusingly, on my white kitchen countertop asking two opposing questions: How could you possibly eat me? And also, paradoxically: How could you not have eaten me all these years?

For most of my adult life, I avoided meat, cheese, butter and cream because they are high in saturated fats, which have long been thought to cause heart disease. Moreover, fats generally are supposed to, well, make you fat. So, like many Americans, I minimized these foods while loading up on vegetables, fruits and grains instead. And, like many Americans, I wasn't getting thinner. Despite rigorous daily jogging and biking, I continually struggled with an extra 10 pounds.

Then, about a decade ago, I took a side job reviewing restaurants for a small local paper in Manhattan. Because the outlet didn't pay for meals, I had to accept whatever free dishes the chefs served me. This turned out not to be the chicken breasts and stir-fried veggies I was accustomed to eating but rather pâté, aged red meats and every kind of luscious cheese, from triple crème to chèvre. I found these heaping dishes of fat-laden food rich, earthy, delicious and—to my surprise—slimming. After two months, I effortlessly lost those stubborn 10 pounds. Moreover, at my annual checkup a few months later, my doctor told me that my cholesterol levels looked fine. Here, then, was a mystery: How could these "bad" foods lead to weight loss and good health? As an investigative journalist, I had to find out.

After spending nine years combing my way through stacks of studies so voluminous they couldn't be crammed into a dozen filing cabinets, I realized that these fats weren't nearly as bad as we've been told. And I wasn't alone. Top scientists in the field reviewing all the data have recently come to the same conclusion, namely that saturated fats cannot be linked to heart disease. Yes, you read that right. And it's a stunning reversal of 50 years of dietary advice. Our fear of meat, butter and cheese dates back only to the 1950s, when one influential scientist, Ancel Keys, Ph.D., proposed that consuming saturated fats leads to heart disease. His science, though, was surprisingly weak: It amounted mainly to a study that was large and pioneering in its day but actually poorly assessed the diets of only a tiny subsample of subjects. This and other flaws weren't understood at the time, however, and in 1961 the American Heart Association issued the country's very first anti-saturated-fat guidelines, thereby launching the diet that health officials still recommend today.

As I researched the question of how one dietary wrong turn could have set our country down a path of mistaken health advice for decades, I began changing my own family's eating habits. My first son had been raised mainly on fruits, grains and vegetables, but after reading studies of how children suffered nutritional deficiencies on low-fat diets, I ramped up the fat. Skim milk was out; whole-fat was back in. Without the fat, your body can't digest the fat-soluble vitamins A and D. And without the latter, the minerals in milk cannot be absorbed. Instead of grains and fruit, my family started eating more cheese. We opted for nuts over crackers; I ordered omelets with the yolks in restaurants.

What pushed me to quit being mostly vegetarian, finally, was the realization that all my squeamish feelings about meat and fat were just a reflection of our current anti-meat moment. A look back in time clearly shows that animal foods were far more favored than they are now. In the Arctic, for instance, in the early 1900s, the Inuit were found to prefer eating the fattiest meat they could while feeding the leaner cuts, including the tenderloin, to their dogs. Across the globe, in 1960s Africa, men of the Masai tribe were observed to consume an average of 3 to 5 liters of milk, or more than a pound of butterfat, per day without any signs of heart disease. They also ate meat, but no vegetables. And while these tribal warriors were definitely more active than an office worker like me, the Masai didn't gain weight upon adopting a more sedentary life in old age.

Inspired partly by these stories, researchers over the past decade have rigorously tested the idea that following a high-fat regimen might actually be healthy. Perhaps, they thought, the pervasive fear that the popular Atkins diet could help people rediscover their waistlines only by sacrificing their arteries wasn't really justified. The results from these recent trials put those cardiovascular worries to rest: They showed not only that a high-fat diet worked best for weight loss, but also that it consistently outperformed a low-fat diet in reducing the risk of diabetes and heart disease. Simply put, I found a high-fat, low-carb diet was healthier.

In practical terms, this means that bacon is all-around better for breakfast than oatmeal. Why? It's thought that the carbohydrates in grains, starchy vegetables, pasta and sugars are uniquely fattening because they cause your body to release insulin, which is the king of all hormones for socking away fat. Meanwhile, the fructose in fruit and high-fructose corn syrup raises triglycerides.

With that kind of solid scientific evidence in hand, I headed to the butcher. One night, I dug up and made my grandmother's brisket recipe. On another, I bought a roast for dinner and browned it in butter—I had learned that butter and lard were the main fats used by American housewives before 1900, long before the epidemics of obesity and diabetes descended upon us.

Soon I felt like a 19th-century housewife myself, with a stewpot continually bubbling on the back burner and a Mason jar full of homemade lard on hand. People used to fry their eggs in the fat left over from cooking bacon, and I did that too. Delicious. And my special low-carb pancakes cooked with lard are exceptionally crispy and light, as my boys, now ages 11 and 7, can happily attest.

It also slowly dawned on me that cooking meat was a more efficient way to get a meal on the table. Making a vegetarian feast for friends, with all the slicing, dicing and roasting, could easily consume the better part of a day. Grilling a steak, by contrast, takes 10 minutes. With a simple green salad, it's not only a complete meal but also one that allows me to enjoy my friends and family. High-fat foods, moreover, tend to be more satiating. While research shows that people can easily consume excessive calories on carbohydrates like pasta and potato chips, it's almost impossible to do so with meat.

It's shocking that meat, cheese and eggs have been unfairly condemned for so many decades based on faulty, unreliable evidence. We are clearly more obese and diabetic for having replaced these foods with high-carb grains and sugar. I don't miss the low-fat life—not the tasteless rice cakes, the salads without dressing, or the dry, skinless chicken breasts. Now I throw two sticks of butter in a pan with a whole chicken, and when all my guests rave about how it's the most delicious bird they've ever tasted, I just smile and tell them, "The secret is not just the butter, but also that it's good for you."