Weight Gain >< Weight Loss
04 December 2008
What Causes Weight Gain?
Whether or not your weight changes depends on a simple rule:
Weight change = calories in - calories out
If you burn as many calories as you take in each day, there's nothing left over for storage in fat cells and weight remains the same. Eat more than you burn, though, and you end up adding fat and pounds. Many things influence what and when you eat and how many calories you burn. These turn what seems to be a straightforward pathway to excess weight into a complex journey that may start very early in life.
Genes:
Some people are genetically predisposed to gain weight more easily than others or to store fat around the abdomen and chest. It's also possible that humans have a genetic drive to eat more than they need for the present in order to store energy for future. This is called the thrifty gene hypothesis. It suggests that eating extra food whenever possible helped early humans survive feast-or-famine conditions. If such thrifty genes still exist, they aren't doing us much good in an environment in which food is constantly available.
Genes:
Some people are genetically predisposed to gain weight more easily than others or to store fat around the abdomen and chest. It's also possible that humans have a genetic drive to eat more than they need for the present in order to store energy for future. This is called the thrifty gene hypothesis. It suggests that eating extra food whenever possible helped early humans survive feast-or-famine conditions. If such thrifty genes still exist, they aren't doing us much good in an environment in which food is constantly available.
Diet:
At the risk of stating the obvious, the quantity of food in your diet has a strong impact on weight. The composition of your diet, though, seems to play little role in weight—a calorie is a calorie, regardless of its source.
Physical activity:
The "calories burned" part of the weight-change equation often gets short shrift. The more active you are, the more calories you burn, which means that less energy will be available for storage as fat. Exercising more also reduces the chances of developing heart disease, some types of cancer, and other chronic diseases.In other words, physical activity is a key element of weight control and health.
The "calories burned" part of the weight-change equation often gets short shrift. The more active you are, the more calories you burn, which means that less energy will be available for storage as fat. Exercising more also reduces the chances of developing heart disease, some types of cancer, and other chronic diseases.In other words, physical activity is a key element of weight control and health.
What Leads to Weight Loss? Just as weight gain is fundamentally caused by eating more calories than you burn, the only way to lose weight is to eat fewer calories than what you burn. People can cut back on calories and lose weight on almost any diet, as long as they stick to it. The real challenge is finding a way to keep weight off over the long run.
Low-fat weight loss strategies don't work for most people.
Low-fat diets are routinely promoted as a path to good health. But they haven't fulfilled their promise. One reason is that many people have interpreted the term "low-fat" to mean "It's OK to eat as much low-fat food as you want." For most people, eating less fat has meant eating more carbohydrates. To the body, calories from carbohydrates are just as effective for increasing weight as calories from fat. In the United States, obesity has become increasingly common even as the percentage of fat in the American diet has declined from 45 percent in the 1960s to about 33 percent in the late 1990s. In South Africa, nearly 60 percent of people are overweight even though the average diet contains about 22 percent of calories from fat.Finally, experimental studies lasting one year or longer have not shown a link between dietary fat and weight. And in the eight-year Women's Health Initiative Dietary Modification Trial, women assigned to a low-fat diet didn't lose, or gain more weight than women eating their usual fare.
Low-carbohydrate, high-protein strategies look promising in the short term.
Another increasingly common approach to weight loss is eating more protein and less carbohydrate. Some of these diets treat carbohydrates as if they are evil, the root of all body fat and excess weight. That was certainly true for the original Atkins diet, which popularized the no-carb approach to dieting. And there is some evidence that a low-carbohydrate diet may help people lose weight more quickly than a low-fat diet, although so far, that evidence is short term.
Why do high-protein, low-carb diets seem to work more quickly than low-fat, high-carbohydrate diets, at least in the short term?
First, chicken, beef, fish, beans, or other high-protein foods slow the movement of food from the stomach to the intestine. Slower stomach emptying means you feel full for longer and get hungrier later. Second, protein's gentle, steady effect on blood sugar avoids the quick, steep rise in blood sugar and just as quick hunger-bell-ringing fall that occurs after eating a rapidly digested carbohydrate, like white bread or baked potato. Third, the body uses more energy to digest protein than it does to digest fat or carbohydrate. No one knows the long-term effects of eating little or no carbohydrates. Equally worrisome is the inclusion of unhealthy fats in some of these diets. If you want to go the lower-carb route, try to include some fruits, vegetables, and whole-grain carbohydrates every day. They contain a host of vitamins, minerals, and other phytonutrients that are essential for good health and that you can't get out of a supplement bottle. Choosing vegetable sources of fat and protein may also lower your risk of heart disease and type 2 diabetes.
Mediterranean-style diets may be effective.
Eating a so-called Mediterranean-style diet—one that includes plenty of fruits and vegetables and that is low in saturated fat but has a moderate amount of unsaturated fat—offers another seemingly effective alternative. In a controlled trial conducted by researchers at Harvard-affiliated Brigham and Women's Hospital, 101 overweight men and women were randomly assigned to a low-fat diet or a Mediterranean-style diet. After 18 months, volunteers on the low-fat diet had gained an average of 6 pounds while those on the Mediterranean diet lost 9 pounds. By the study's end only 20 percent of those in the low-fat group were still following the study diet, compared to more than half of those on the Mediterranean-style diet.
Low-fat weight loss strategies don't work for most people.
Low-fat diets are routinely promoted as a path to good health. But they haven't fulfilled their promise. One reason is that many people have interpreted the term "low-fat" to mean "It's OK to eat as much low-fat food as you want." For most people, eating less fat has meant eating more carbohydrates. To the body, calories from carbohydrates are just as effective for increasing weight as calories from fat. In the United States, obesity has become increasingly common even as the percentage of fat in the American diet has declined from 45 percent in the 1960s to about 33 percent in the late 1990s. In South Africa, nearly 60 percent of people are overweight even though the average diet contains about 22 percent of calories from fat.Finally, experimental studies lasting one year or longer have not shown a link between dietary fat and weight. And in the eight-year Women's Health Initiative Dietary Modification Trial, women assigned to a low-fat diet didn't lose, or gain more weight than women eating their usual fare.
Low-carbohydrate, high-protein strategies look promising in the short term.
Another increasingly common approach to weight loss is eating more protein and less carbohydrate. Some of these diets treat carbohydrates as if they are evil, the root of all body fat and excess weight. That was certainly true for the original Atkins diet, which popularized the no-carb approach to dieting. And there is some evidence that a low-carbohydrate diet may help people lose weight more quickly than a low-fat diet, although so far, that evidence is short term.
Why do high-protein, low-carb diets seem to work more quickly than low-fat, high-carbohydrate diets, at least in the short term?
First, chicken, beef, fish, beans, or other high-protein foods slow the movement of food from the stomach to the intestine. Slower stomach emptying means you feel full for longer and get hungrier later. Second, protein's gentle, steady effect on blood sugar avoids the quick, steep rise in blood sugar and just as quick hunger-bell-ringing fall that occurs after eating a rapidly digested carbohydrate, like white bread or baked potato. Third, the body uses more energy to digest protein than it does to digest fat or carbohydrate. No one knows the long-term effects of eating little or no carbohydrates. Equally worrisome is the inclusion of unhealthy fats in some of these diets. If you want to go the lower-carb route, try to include some fruits, vegetables, and whole-grain carbohydrates every day. They contain a host of vitamins, minerals, and other phytonutrients that are essential for good health and that you can't get out of a supplement bottle. Choosing vegetable sources of fat and protein may also lower your risk of heart disease and type 2 diabetes.
Mediterranean-style diets may be effective.
Eating a so-called Mediterranean-style diet—one that includes plenty of fruits and vegetables and that is low in saturated fat but has a moderate amount of unsaturated fat—offers another seemingly effective alternative. In a controlled trial conducted by researchers at Harvard-affiliated Brigham and Women's Hospital, 101 overweight men and women were randomly assigned to a low-fat diet or a Mediterranean-style diet. After 18 months, volunteers on the low-fat diet had gained an average of 6 pounds while those on the Mediterranean diet lost 9 pounds. By the study's end only 20 percent of those in the low-fat group were still following the study diet, compared to more than half of those on the Mediterranean-style diet.
Lessons from Losers
Since 1993, more than 5,000 women and men have joined the National Weight Control Registry. This select "club" includes only people who lost more than 30 pounds and kept them off for at least a year. What was their secret?
They exercised.
Registry participants burn an average of 400 calories per day in physical activity. That's the equivalent of about 60 to 75 minutes of brisk walking, or 35 to 40 minutes of jogging.
They ate fewer calories.
On average, registry volunteers consume about 1,400 calories a day. That's significantly less than the calories consumed by the average American. This doesn't mean, however, that you should aim for 1,400 calories a day. What's right for you is based on your weight, height, and activity level.
Registry participants burn an average of 400 calories per day in physical activity. That's the equivalent of about 60 to 75 minutes of brisk walking, or 35 to 40 minutes of jogging.
They ate fewer calories.
On average, registry volunteers consume about 1,400 calories a day. That's significantly less than the calories consumed by the average American. This doesn't mean, however, that you should aim for 1,400 calories a day. What's right for you is based on your weight, height, and activity level.
They watched less television, limited fast food intake, cut back on sugars and sweets, and ate more fruits and vegetables.
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