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"Finally, amidst the sea of baseless fad diet books lining bookstore shelves, you have a weight loss guide formulated from rigorous scientific research and sound evidence.... I plan to use this diet plan with my patients!"—-Janet Bond Brill, PhD, RDN, nationally recognized nutritionist and author of three books on cardiovascular disease prevention
"Dr. Varady's rigorous studies of alternate-day fasting have established its powerful ability to promote weight loss. The Every-Other-Day Diet is an authoritative description of how and why alternate-day fasting is beneficial, providing guidelines and practical advice for incorporating intermittent fasting into one's weekly routine."—-Mark Mattson, PhD, chief of the Laboratory of Neurosciences at the National Institute on Aging,
professor of neuroscience, Johns Hopkins University
The New Science of Every-Other-Day Dieting
Study after study shows the Every-Other-Day Diet really works
When it comes to health and wellness, there's a reason we look to the accuracy and authority of scientific experiments to help us suss out what's truly useful and sound information from all of the baseless, specious, and fad claims and advice out there—to separate the proverbial wheat from the chaff: Scientific experiments aren't based on hype and hope.
A well-designed, well-conducted scientific experiment helps separate truth from wishful thinking, fact from fantasy. And a series of scientific experiments, testing the same theory and generating the same results (what scientists call replicating a scientific finding), creates a body of knowledge you can trust and then act on.
Given the importance of weight loss to our health and well-being, to preventing and reversing disease, and to restoring self-esteem, you'd think most diet books would be packed with scientific evidence that justifies their approach. But that's not the way it is.
Yes, there have been scientific studies on a few popular diet plans. For example, a study published in the Journal of the American Medical Association showed that overweight and obese women on the Zone Diet, the low-carb Atkins Diet, or the low-fat Ornish Diet lost a little bit of weight after one year of dieting—an average of 3.5 pounds on the Zone Diet, 4.8 pounds on the Ornish diet, and 10.4 pounds on Atkins. (Yes, that's after dieting for one year. I think you'll do a lot better on the Every-Other-Day Diet.) However, most popular weight-loss plans don't have any scientific support for their approach. None. Zero. Zilch.
Why am I making such a big fuss over scientific support for the diet plans in diet books? Because the Every-Other-Day Diet does have a significant body of scientific research behind it. To date, I've conducted seven clinical trials involving nearly 400 people, and I have published the results in 20 scientific papers. My studies have shown, again and again, that the Every-Other- Day Diet works. The people in my studies lose weight. And in my ongoing, three-year study on weight maintenance sponsored by the National Institutes of Health, EOD dieters are keeping the weight off.
In other words, the Every-Other-Day Diet is a research-proven diet that you can trust. If you follow this diet, eating 500 calories on Diet Day and whatever you want on Feast Day, the scientific evidence says you will lose weight. And if you go on the maintenance program described in chapter 7, the Every-Other-Day Success Program, my newest findings show you will keep the weight off.
I know the Every-Other-Day Diet may seem too good to be true. I know you might be asking yourself, "Can I really lose weight eating anything I want, every other day?" Never fear. You can. And not just because I say so—because nearly a decade of rigorous scientific research says so. And since your trust in the science-proven effectiveness of the Every-Other-Day Diet is so important to me, I've devoted this chapter to sharing the research and studies that support my claims. I want you to know—really know—that the diet you're about to undertake isn't a novel idea that's never been put to the test. It's not based only on the experience of patients in one doctor's practice (which is the case with many diet plans). And it's not theoretical—an idea that seems to make metabolic and biological sense, but has little real-world evidence to show that it works.
By learning about the science of every-other-day dieting and by reading about my studies and their positive findings, you can embark on this new weight-loss program with confidence, conviction, and enthusiasm. So let's start at the beginning: with my discovery of this diet, in the basement of a building on the campus of the University of California, Berkeley, where, in 2006, I was a postdoctoral fellow.
The Mice That Always Lost Weight
After I graduated from McGill University in Canada with my PhD in nutrition, I moved to California to do postdoctorate research in the Department of Nutritional Science at Berkeley. (A native Canadian, I was delighted to discover that "winter" in Northern California is just a series of rainstorms and that daffodils bloom in February!)
Under the guidance of my advisor, Dr. Marc Hellerstein, I investigated the effect of calorie restriction on cancer. There was already a lot of research on calorie restriction and longevity in animals; it showed that when mice are fed less food, they live up to twice as long as mice fed a normal diet. Furthermore, some of the biochemical mechanisms triggered by calorie restriction in longevity research are known to be anticancer. The mechanisms include slower cell division; lower levels of IGF-1 (insulin-like growth factor 1, a growth factor that stimulates cancer cells to divide and multiply); and lower levels of glucose, the main fuel for cancer cells.
Our research question was this: Can you put a mouse on the ultimate form of calorie restriction—fasting—so that the growth of cancer cells is slowed, but the animal does not lose weight? (In their research, scientists are always trying to isolate and analyze specific factors. In this case, we wanted to isolate the effect of calorie restriction on cancer from the effect of weight loss on cancer.)
But as hard as we tried, we couldn't keep the mice from losing weight! We fasted them one day and let them eat all they wanted the next day. But they never ate enough calories on "feed day" to fully compensate for the total lack of calories on "fast day." Sometimes they managed to eat 150% of a normal day's calories on feed day. Sometimes they ate up to 170%. But they never ate 200% of their normal caloric intake on feed day to make up for the zero calories on fast day. And so they always lost weight.
My experiment had failed because there was no way to separate the effect of calorie restriction from the effect of weight loss. I was not a happy scientist! But a scientific investigation that seems like a dead end can suddenly present a new vista of opportunity. And that's just what happened: I had a eureka moment, an Aha!, a conceptual breakthrough when I realized that the mice always lost weight on alternate-day fasting. The mice always lost weight. Could alternate-day fasting help us humans lose weight? If people fasted one day and then ate all they wanted the next day, would they always lose weight, just like the mice?
The concept of the Every-Other-Day Diet—using alternate-day fasting for weight loss—was born. It was time for me to say good-bye to the mice in the basement at Berkeley and move to Chicago, where I had been hired as an assistant professor in the Department of Kinesiology and Nutrition at the University of Illinois at Chicago. There, I started conducting studies on weight loss. With people.
The Magic Number
When I looked closely at the scientific literature on alternate-day fasting for cancer and heart disease—studies conducted exclusively on animals in the laboratory—I found that many of the risk factors for the two diseases were lowered most effectively when the animals ate only 25% of their normal calories on fast day. Not 75%. Not 50%. Not 0%, or a total fast. Time and again, the healthiest percentage was 25%, or what I call a modified fast.
And the 25% level of calories on fast day did more than prevent and reverse signs of disease. It also prevented the loss of muscle mass the animals otherwise had experienced at 0%, when they were given no food on fast day.
Why was that important? Losing muscle mass while dieting is a disaster for weight loss and weight maintenance. That's because muscle (lean body mass, in scientific terms) is metabolically active tissue that burns a lot of calories. Lose muscle during dieting and you'll burn fewer calories after dieting and regain your weight—as fat! This is perhaps the key reason why 5 out of 6 people who lose weight gain it all back (and then some). So I decided that on fast day—the day called Diet Day in the Every-Other-Day Diet—people would eat 25% of their normal caloric intake, or about 500 calories. I was ready to recruit participants and begin my study.
At this point, I have to make an embarrassing confession: even though I was about to conduct a study on every-other-day dieting in people, I didn't think the diet would work!
Why not? Well, many overweight people eat around 3,000 calories a day, and I couldn't imagine they'd be willing or able to eat only 500 calories every other day. And then there was my conversation at a medical conference with Dr. Eric Ravussin, PhD, director of the Nutrition and Obesity Research Center at the Pennington Biomedical Research Center at Louisiana State University. I told him I was thinking of conducting a study on alternate-day fasting for weight loss, allowing my participants to eat 500 calories on fast day.
"Don't even bother," he said. And then he proceeded to tell me (to my surprise) that he and his colleagues had recently conducted a human study on alternate-day fasting, in which the participants ate zero calories on fast day. A study that didn't go too well. First, he wasn't able to recruit anyone from outside Pennington to participate in the study, because the idea of fasting every other day seemed so onerous; he was forced to enroll Pennington professors in the study. Next, he couldn't even convince many of those professors to participate for all three weeks of the study. Of the 16 that started, only 8 finished. And even those who finished told him they hated alternate-day fasting. Their families hated it, too. "I was so cranky and irritable on fast day that my wife wouldn't talk to me," said Dr. Ravussin, who participated in his own study.
I had already planned to allow my study participants to eat 500 calories on fast day; my conversation with Dr. Ravussin convinced me I'd made the right decision. For successful every-other-day dieting, you need to be on a modified fast, not a total fast. (In scientific papers, I sometimes call my approach ADMF, or alternate-day modified fasting.) You need to eat a small meal during the day, so you can stay balanced emotionally and mentally, interact with people without blowing a fuse, and get through your workday efficiently and effectively.
In spite of my doubts, I went ahead with my study, recruiting people who were normal weight and overweight (not obese). My goals for the study were broad: to find out if anyone could actually stay on the diet for a few months, and if they would lose weight. Much to my surprise, they did both!
There were 32 people in the original study. Sixteen went on the Every-Other-Day Diet. The other 16 were the control group—they didn't diet or change their eating habits at all. After three months, my colleagues and I compared the two groups. Not surprisingly, people in the control group didn't lose any weight. But all of the every-other-day dieters shed pounds.
The folks who were normal weight at the start of the diet lost an average of 11.9 pounds after three months. Those who were overweight lost an average of 11 pounds. (A few of them lost as much as 25 pounds.) The overweight group also saw significant drops in bad cholesterol (low-density lipoprotein, or LDL) and in high blood pressure. And most of the participants said they didn't find the diet difficult at all.
I had proven to myself that every-other-day dieting was a reasonable, effective approach to weight loss. People could eat 500 calories every other day on Diet Days, without difficulty. People could eat whatever they wanted on Feast Day and still lose weight.
As you can imagine, I was very excited about this first set of results. After all, just about everybody hates daily dieting. Don't you? You hate the endless weeks and months of nonstop deprivation. You hate the constant hunger. You hate the complicated requirements and rules. That's why you've probably quit most of the diets you've started. Who wouldn't? Daily dieting is a drag. But every- other-day dieting is a new and effective way for people to lose weight—without deprivation, without hunger, without rigid rules.
After the success of this first study, there were many other questions about every-other-day dieting that I wanted to answer, with detailed, careful, and repeated research:
Would the diet work on the obese, or would they binge on Feast Day?
How hungry would obese people be on the diet? So hungry they couldn't help but overeat?
Could people exercise on Diet Day? And would they overeat when they exercised?
Would the diet work if you ate high-fat food? Or was low-fat food the only way to go?
How would the diet affect risk factors for heart disease like total cholesterol, LDL cholesterol, HDL cholesterol, and high blood pressure?
How would the diet affect hormones like leptin, which play such a key role in appetite?
Was there a way for people who lost weight on the Every-Other-Day Diet to maintain their weight loss?
Nearly a decade later, after six more studies on people and more than 20 published scientific papers on every-other-day dieting, I'm proud and delighted to say that these questions have been answered. In fact, it's only because they were answered that I feel comfortable presenting the Every- Other-Day Diet to the tens of millions of people who really want to lose weight and keep it off and not just be disappointed by another every-day diet.
Let's take a closer look at a few of my studies and what I discovered. To make it easier for you to follow the trail of my research, I've listed the year each study was published, the journal it was published in, and the specific findings of the study.
Body Mass Index—The Way Scientists Measure Overweight
As you read the studies in the rest of the chapter, you'll encounter several common terms: normal weight, overweight, and obesity. However, nutritional scientists and other health experts use these terms in a very specific way: to indicate the level of body mass index, or BMI, a standard measurement of body fat. The three main categories of BMI are
Normal weight: BMI of 18.5 to 24.9
Overweight: BMI 25 to 25.9
Obese: BMI 30 and above
How do these three levels of BMI translate into actual pounds? Here are two examples: A 5'4" woman is normal at 130 pounds, overweight at 145 pounds, and obese at 174 pounds. A 5'10" man is normal at 160 pounds, overweight at 174 pounds, and obese at 209 pounds.
To figure out your BMI, use the BMI calculator at the website of the Centers for Disease Control and Prevention:
Just enter your height in feet and inches, and your weight, and then hit the "Calculate" button. I'm happy to say my BMI is 21.6; my coauthor Bill's is 22.4. The Every-Other-Day Diet for weight loss, and the Every-Other-Day Success Program for weight maintenance, which you'll read about in chapter 7, helps both of us stay in the normal range.
2009, American Journal of Clinical Nutrition
The Every-Other-Day Diet works and is super-healthy, too!
A study in the American Journal of Clinical Nutrition was the first to definitively show that every-other-day dieting works to help obese people lose weight.
My colleagues and I studied 16 obese people, 12 women and 4 men, with an average weight of 213.4 pounds and an average BMI of 33.8. All of them went on the diet for two months. For the first month, they ate frozen and other packaged foods for their 400-to 500-calorie lunches and 100-calorie snacks on Diet Day. (We distributed the lunches and snacks on a weekly basis.) For the second month, they prepared the Diet Day lunches and snacks themselves, after meeting with a nutritionist on our staff who counseled them about the calorie level of Diet Day and the foods and portion sizes that would help them stay at that level. (You'll find all the practical details for Diet Day in chapter 2.)
An average of 12 pounds of weight loss. After two months, the average weight loss was 12.3 pounds, a steady, healthy weight loss of 1.5 pounds per week. And the rate of weight loss was just about the same whether the participants were given frozen and packaged food or they prepared their own food. They just kept losing pounds, week after week.
Excerpted from The Every-Other-Day Diet by Krista Varady. Copyright © 2013 Krista Varady. Excerpted by permission of Hyperion.
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