Read an Excerpt
The Calcium KeyThe Revolutionary Diet Discovery That Will Help You Lose Weight Faster
By Michael Zemel Bill Gottlieb
John Wiley & SonsISBN: 0-471-46368-X
Chapter OneDiscovering the Calcium-Fat Connection
Susan's Story: 48 Pounds Lost
Susan is a foster parent who cooks and cares for four children. With the intense stress of her daily life, she found it extremely difficult to lose weight. But the 45-year-old didn't have any problem shedding pounds as soon as she went on the Calcium Key Weight-Loss Plan.
"This was the easiest, nondreading-it diet I've ever been on," she told me. Susan found the diet easy to understand and easy to follow. She could eat all the regular foods she normally ate, even fried chicken. She could cook for herself, her husband, and her kids at the same time, just as long as she counted her exchanges. When she felt hungry between meals, she would grab a carrot or fruit or other low-calorie but filling food. And she used fruit-flavored yogurt to satisfy her sweet tooth so that she didn't eat too much candy or cake.
Susan, who is 5'9", lost 48 pounds on the Calcium Key Weight-Loss Plan, going from 201 to 153 pounds. Susan had a lot of fun losing weight. Everybody at her church noticed how much weight she'd lost. They asked her whether she was on a diet. And she laughed and said, "No, I'm just eating right and drinking a lot more milk!"
Her husband is Susan's biggest supporter. Just about every day he looksat her and says, "Honey, you're looking good."
Since grade school, you've been told that calcium is good for your teeth and your bones. You know that. Everybody knows that.
But what you may not know is that calcium is good for a lot more than a bright smile and a healthy skeleton. If you didn't have enough of this mineral circulating in your bloodstream, here's what would happen:
Your heart wouldn't beat.
Your blood wouldn't clot.
Your hormones wouldn't send the chemical messages that regulate a wide range of metabolic functions in your body, from temperature to appetite to sleep.
Your nerves wouldn't transmit electrical signals-you wouldn't move a muscle, digest food, or perform any action.
Calcium is so critical to your body's moment-to-moment functioning that when blood levels drop below the amount required by your cells, one of your body's possible responses is to steal calcium from its crystalline home in the bones. Sure, you can end up with osteoporosis, the bone-thinning disease. But you're still alive-and that's your body's first priority.
Calcium is a necessity for life, which is one of the reasons I've spent most of the 25 years of my scientific career studying this fascinating mineral. I wanted to know exactly how the body manages to retain or lose calcium. And I wanted to know exactly how this crucial nutrient functions in health and disease.
This chapter is the story of the quest for more knowledge about calcium-and better health for everyone. Step by step, year by year, this quest has led me and my fellow researchers to discover a role for calcium that neither we nor any other scientist ever expected to find: along with its other crucial functions within the cells of the body, calcium affects fat cells, regulating how much fat is made, how much fat is stored, and how much fat is burned.
In this chapter, I'll tell you about this discovery and all that it means for your quest for permanent weight loss. But first, I want you to understand the biochemical mechanisms by which calcium helps control weight. That way, when you begin to follow the recommendations of the Calcium Key Weight-Loss Plan, you won't have any doubts about the scientific efficacy of what you're doing. You'll know that the Calcium Key Weight-Loss Plan will work, because you'll have seen for yourself that study after published scientific study-over 40 in all-have proven that it works.
This is the story of the discovery of the missing link in weight loss: the story of calcium and fat cells, particularly of how high-calcium foods like dairy products can change the metabolism of fat cells, helping you to prevent weight gain or to shed extra pounds. The story begins with an investigation into an area seemingly unrelated to calcium and overweight (but that actually is directly connected): high blood pressure, or essential hypertension.
The Calcium Paradox
The first hint of a cause-and-effect relationship between calcium and high blood pressure came in the 1960s. Scientists discovered that people who drank water that contained a lot of calcium carbonate (hard water) had fewer heart attacks and strokes than people who drank water with very little calcium carbonate (soft water). High blood pressure is a risk factor for both of these diseases. Scientists asked themselves if calcium could be protecting people against high blood pressure.
Two Landmark Studies
In the early 1980s, David McCarron, M.D., professor of medicine at Oregon Health Sciences University in Portland, published two landmark papers on calcium and high blood pressure in Science, revolutionizing the way other scientists thought about this connection.
In a 1982 study, McCarron and a team of researchers looked at the dietary calcium intake of people with and without high blood pressure. They found that those with high blood pressure consumed an average of 668 milligrams (mg) of calcium, while those without the problem consumed 886 mg. "The data suggest that inadequate calcium intake may be a previously unrecognized factor in the development of hypertension," McCarron wrote.
In a 1984 study, McCarron and his colleagues analyzed nutritional data from the government's first massive survey of America's eating habits: the National Center for Health Statistics, Health and Nutrition Examination Survey, or NHANES-1. He looked at the link between the intake of 17 different nutrients and blood pressure levels in more than 10,000 men and women. The most significant link: calcium. The lower the level of calcium in the diet, the greater the risk of developing high blood pressure.
During the following two decades, dozens of other scientific studies confirmed the link between calcium and high blood pressure. They showed that many people can reduce hypertension by having a daily calcium intake of 1000 to 1500 mg. They also showed that calcium from food has about twice the pressure-lowering power as calcium from supplements. I'd like you to remember this important point.
Frank's Story: Losing Those Love Handles
Frank is a 47-year-old executive for a trucking company. His best experience of being on the Calcium Key Weight-Loss Plan was when his wife first noticed that he was losing weight around his midsection.
Frank's experience is similar to that of many men and women who go on the plan. Soon they (and their near-and-dear) start to experience a unique benefit: less abdominal fat. Love handles, stomach flab, a beer belly-whatever you want to call it-the plan can make it melt away.
Frank didn't only lose his gut. He lost 26 pounds, dropping from 220 to 194. Before being on the Calcium Key Weight-Loss Plan, Frank had never been able to lose weight. Once on the plan, he found it easy to shed pounds. One big change in his eating style that really helped was that instead of getting hungry and gorging himself at the next meal, he ate between-meal snacks of cheese or yogurt, satisfying his appetite.
His wife felt satisfied, too. For years, she'd been after Frank to do something about his weight. But the self-confessed procrastinator had never felt motivated to discipline his eating habits. With the Calcium Key Weight-Loss Plan, he didn't have to. He told me he just followed the exchange system and added dairy.
Frank felt kind of bad about himself when he started the plan. He was just too fat for his own liking. But now he feels good about himself. He lost weight-something he never thought he'd be able to do.
At the time McCarron's research appeared, I was an associate professor at Wayne State University in Detroit. And I was immediately interested in trying to discover the mechanism of calcium's effect on blood pressure, specifically how the nutrient worked to improve health. This task was complicated by the calcium paradox of essential hypertension.
The source of the paradox: at the same time that McCarron was discovering that a calcium-rich diet could protect against high blood pressure, doctors were writing millions of prescriptions for calcium channel blockers-drugs that treat high blood pressure by blocking the entrance of calcium into the cells. The drugs work because when calcium enters the smooth muscle cells of an artery, it causes the artery to constrict or narrow, raising blood pressure. Blocking calcium from entering the cells keeps the arteries wider and blood pressure normal.
How could both of these realities exist simultaneously? How could increasing calcium in the diet make blood pressure go down, while increasing calcium in the cells make blood pressure go up?
My colleagues and I-and other researchers, such as Lawrence Resnick, M.D., professor of medicine at the Hypertension Center at the New York Weill Cornell Medical Center in New York City-knew that if we were to solve this paradox, we had to discover a mechanism whereby increasing calcium in the diet decreased calcium in the cells. Either we had to find a factor that pushed calcium into the cells-a factor removed by a high-calcium diet-or we had to find a factor that blocked calcium from entering the cells-a factor released by a high-calcium diet.
The Unexpected Role of the Hormone Calcitriol
Calcium plays a crucial role in regulating the core functions of the body. Needless to say, the body has evolved mechanisms to guarantee that blood calcium levels never drop too low. The main mechanism is hormonal. If calcium levels fall-if you eat a low-calcium diet, for example-the parathyroids, small glands on the surface of the thyroid gland, secrete parathyroid hormone (PTH). In turn, PTH triggers the release of another hormone, calcitriol.
Calcitriol helps your body make the best use of calcium. It increases absorption in the intestines, so you get the most calcium possible from food. And it increases reabsorption from the kidneys, so you lose as little as possible through excretion.
In our research, we focused on calcitriol as the factor that might be responsible for the calcium paradox. And in the laboratory, using animal models of human hypertension, we and other researchers found something we never expected to find. Calcitriol didn't only act on the cells of the intestines and the kidneys to help the body absorb and retain calcium. It also acted on the smooth muscle cells of the arteries, allowing calcium to move into these cells, thereby raising blood pressure. The calcium paradox of essential hypertension had been resolved. It turned out that
1. Low dietary levels of calcium cause an increase in the body's manufacture of calcitriol. Higher levels of calcitriol cause more calcium to enter the smooth muscle cells of the arteries. More calcium in these cells causes the arteries to narrow, raising blood pressure.
2. High dietary levels of calcium cause a decrease in the body's manufacture of calcitriol. Lower levels of calcitriol cause less calcium to enter the smooth muscle cells of the arteries. Less calcium in these cells keeps the arteries relaxed, maintaining normal blood pressure.
In the 1990s, this discovery about calcitriol and calcium levels in smooth muscle cells would play a crucial role in the scientific discovery of calcitriol and calcium levels in fat cells.
Studying a Salt-Sensitive Population
Low calcium intake isn't the only reason people get high blood pressure. Many different factors can cause it. That's why there are so many different types of drugs available to treat high blood pressure-each targets a different factor. My colleagues and I were interested in investigating several of these factors and discovering if calcium was the link between them.
For example, we were studying insulin resistance. In this problem, the hormone insulin is less effective than it should be in ushering blood sugar into cells; insulin resistance is often the first stage in the development of type II (adult-onset) diabetes. People who are insulin resistant also tend to be overweight, have higher than normal levels of the blood fat triglycerides, and have high blood pressure. This is a grouping of problems that Gerald Reaven, M.D., professor at Stanford University School of Medicine, has called syndrome X, which is also referred to as the insulin resistance syndrome and the metabolic syndrome. I wondered if there was a connection among all of the problems of the metabolic syndrome.
As part of our effort to answer this question, we conducted a study of African-American men with high blood pressure. African-Americans, like people over 60, are known to be salt-sensitive. In general, when they eat too much salt, their bodies excrete more calcium, which sparks an increase in PTH, increasing calcitriol and increasing blood pressure. For African-Americans and those over 60, calcium is often an excellent treatment for high blood pressure. Could it also treat insulin sensitivity?
In our study, we gave African-American men 2 cups of low-fat yogurt a day, increasing their daily calcium intake from 400 mg to 1000 mg. After a year, we had results.
On average, blood pressure fell and insulin resistance normalized. But there was a result we didn't expect: the men lost an average of 11 pounds of body fat.
I had no explanation for this result. In fact, it made no sense to me whatsoever. Why did they shed fat and gain muscle? They didn't eat fewer calories. They didn't exercise more. I decided it was just one of those stray observations that should go unpublished-the result of chance rather than any scientifically verifiable factor.
But even though I never published the result, that didn't stop me from talking to other scientists about it. And frequently researchers would tell me that they had conducted a study in which they also saw a direct relationship between dietary calcium and body fat-that is, higher calcium intake, lower fat-but because they couldn't explain the result, they didn't publish it.
It made me think that this wasn't just some random observation. There really was something going on. Little did I know that my colleagues and I had put together the first piece of the puzzle-the calcitriol connection.
Excerpted from The Calcium Key by Michael Zemel Bill Gottlieb Excerpted by permission.
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