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Fat Fast versus Atkins phase one: Jump-starting low carb high fat weight loss

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What's the best approach to jump-starting weight loss on a low carb high fat diet? A concept known as a Fat Fast, which Dr. Robert Atkins popularized, is still used. But how does it compare with phase one of the Atkins diet? I interviewed several experts to get their views:

First, let's start with the Atkins diet phase one. It features several phases, with the first one, the induction phase, designed to put you into nutritional ketosis. You eat moderate protein, more healthy fats and also get fiber in the form of vegetables. Learn about the different phases by clicking here.

But a Fat Fast takes a different approach. Dana offers this explanation:

“The Fat Fast is based on the work of Kekwick and Pawan, who, in 1956, published research in the prestigious journal The Lancet detailing their work regarding the idea that “a calorie is a calorie is a calorie. First, they took a group of obese subjects and put them on balanced diets with differing calorie counts – 2000, 1500, 1000, or 500 calories per day. Unsurprisingly, the subjects who ate the fewest calories lost the most weight.”

And then came the test: “Kekwick and Pawan put all their subjects on the same number of calories – 1000 per day. But varied the macronutrient composition of the diets – either a balanced diet, or 90% of calories from carbohydrates, 90% of calories from protein, or 90% of calories from fat. The results were groundbreaking. On 1000 calories per day, 90% from carbohydrate, subjects actually gained a little weight. On 1000 calories of a mixed diet, they lost a little, and on 1000 calories, 90% from protein, they lost substantially more. But the most rapid weight loss by far happened when subjects ate 1000 calories per day, 90% from fat.”

How this works: “Apparently when the body is fed mostly fat, and very little carbohydrate, it is very quickly forced into burning almost all fat for fuel. Coupled with caloric limitation – 1000 calories per day – this stimulates the body to turn from dietary fat to stored body fat. (By contrast, if the body is burning glucose for fuel, and doesn’t have a sufficient supply from food, it will break down muscle to convert into glucose.) Furthermore, creating this ketogenic, fat-burning state has been demonstrated to defend muscle mass. In the 1960s, Dr. Frederick Benoit put 7 obese men on a total fast – the “no calorie diet,” you might call it. If it’s all about calories in, calories out, this should be the best fat loss diet possible. In 10 days of fasting, the subjects lost an average of 21 pounds. This sounds great, until you learn that only 7.5 pounds of that, on average, were fat. The rest was lean body mass.”

Consequently, “Benoit then put his subjects on 1000 calories per day, 90% of them from fat – a very low calorie diet for adult men, no doubt, but still considerably more calories than before. What happened? In ten days, they lost an average of 14.5 pounds, with only 0.5 pounds of it, on average, being muscle mass. They’d lost twice as much fat eating 1000 calories per day of fat than they had eating nothing at all.”

Sound impossible? No, says Dana: “It appears to be the combination of forcing the body into a fat-burning metabolism while simultaneously cutting calories pretty strictly that results in the very rapid fat loss. I generally lose a pound a day when I Fat Fast.”

However, “Dr. Robert Atkins, author of “Dr. Atkins’ New Diet Revolution,” recommended the Fat Fast for people who are metabolically resistant to weight loss. He prescribed the same formula as Kekwick and Pawan,and Benoit: 1000 calories per day, 90% of them from fat. He suggested cream cheese, macadamia nuts, tuna salad made with triple the usual quantity of mayonnaise, things like that. He instructed the reader to divide this into 5 small feedings per day, of 200 calories each. Being a cook to the core, I had to play with it; that’s the genesis of The Fat Fast Cookbook.”

Jimmy says: “By definition, here is the Fat Fast:

- 1,000 calories per day
– 90 percent of calories come from dietary fat
– Eat five 200-calories “meals” every 3-4 hours”

Can a Fat Fast ever be helpful? Well, maybe, he adds:

“For people who have gone on a low-carb diet and are for one reason or another struggling to get into nutritional ketosis. For most people, finding their personal carbohydrate tolerance level, individualized protein threshold level, and eating dietary fat, especially saturated and monounsaturated fat, to satiety will make this happen. But for some people who haven’t found their sweet spot, a Fat Fast could be one way to help them jumpstart that process.”

However, if you’re already gotten into nutrition ketosis, Jimmy notes: “My personal experience with a Fat Fast after being keto-adapted and already eating a lot of fat was horrendous.

“My normal caloric load in my diet is around 2100-2500 calories. So my calorie intake dropped by more than half. And since I could only eat 1000 calories a day, that meant a lot of the dietary fat that I was consuming in my diet was reduced despite the high percentage of fat you eat in Fat Fast. My big concern is why EVERYONE needs to drop to 1000 calories a day to do this. My wife Christine usually has 1600 calories a day, so when she went on a Fat Fast dropping down to 1000 it wasn’t as profound as what I went through. I’m all for people trying what might help them get into a state of ketosis, but be wary that this isn’t some magical method for doing it.”

And be sure to choose what Jimmy calls “fatty sources of protein.” Translation: “NO lean meats like chicken breast or turkey. Leave the fat on the animal food and that’s a fatty source of protein. Many butchers just chop off the fat because they think that’s what consumers want.”

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