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Some of the reasons people are over-fat are under their control, and some aren't. Some reasons are obvious, and some are not so apparent. Here are the facts you should know about your body's fat-storing habits.
Heredity. Do fat parents usually produce fat children? Statistics say yes. Lean parents have only a seven percent chance of having an obese adolescent. If one parent is obese, there is a forty percent chance their child will be obese. If both parents are obese, the probability of the child's being obese may be as high as eighty percent. Genes may actually be a more powerful determinant of obesity than diet. Studies on adopted children show that these children's body weight tends to be more like their biological parents than their adopting ones. Studies of identical twins reared in different environments with different parental eating habits showed a tendency toward similar fatness or leanness. But, don't be too quick to blame your parents. Genes influence whether or not children or adults become fat, but diet and lifestyle, both of which are under your control, also play a role. It's what you do with the genes you inherit that determines whether you will wind up fat or lean.
Are fat children more likely to become fat adults? Yes and no. One study showed that nine out of ten obese infants became lean by the time they were seven. Yet, obese infants are still three times more likely to be fat at age seven than infants who have been lean from the start. Studies have also shown that forty percent of obese seven-year-olds are likely to become obese adults, seventy percent of obese preteens are likely to become obese adults, and around eighty percent of obese adolescents are obese as adults. The fatter children are in the first few years of life and the longer they keep their excess fat, the greater the likelihood they will remain fat into adolescence and adulthood.
Does overeating lead to overfattening? Most studies show that fat children and adults do not eat more than lean ones, some may even eat less. What's significant, however, is that while fat persons do not necessarily eat more food, they do eat more calories than they burn off in exercise. The fat person may also have a slower metabolism than the lean person. Also, studies show that fat persons are more likely than lean persons to eat foods higher in fat. They may get around forty percent of their calories from fat instead of the recommended 20-25 percent.
A fat calorie is heavier than a protein or carb calorie. It's a myth that a calorie is a calorie is a calorie. Calories from fat are more fattening than calories from proteins or carbohydrates. Our bodies tend to store excess calories from fat as fat more readily than they do excess calories from carbohydrates or proteins. Not only does the body store fat calories more easily, it also burns them less readily. The body, plotting to protect itself from starvation, will use up carbohydrate stores for energy before dipping into the fat reserves. And the body must use more energy (or calories) to metabolize carbohydrates and proteins than it uses to burn fats. Fatty foods tend to pack more calories into a smaller volume than do carbohydrate and protein foods. Because the stomach takes its cues for fullness based upon food volume rather than calories, gram for gram fat is less satisfying.
Sugar can make you fat, too. The hormone insulin doesn't just control sugar, it also controls fat. Insulin also helps the body store excess sugar as fat. Junk sugars and other carbohydrates with a high glycemic index are the most likely to be stored as fat. Insulin bursts following the ups and downs of blood sugar also contribute to fat storage, which is why five mini meals a day that keep your blood sugar steady are more likely to keep you lean than three big binges. Once you get overfat from sugar, a vicious cycle may begin according to a new metabolic theory called insulin resistance.
This is how I.R. works: when sugar enters the bloodstream, the pancreas secretes a dose of insulin high enough to usher the sugar into the muscle cells and other organs where it's needed for energy. If a lot of sugar enters the bloodstream, the pancreas releases a lot of insulin. Some people develop a metabolic quirk in which the cells begin to resist the insulin. Since glucose levels in the blood are not dropping, the body secretes even more insulin, which can cause two problems: the overworked pancreas may gradually wear out, resulting in diabetes, and the excess insulin promotes more fat storage. This concept of insulin resistance also explains why some people become fat, even though they really do not take in too many calories. They just eat too many carbohydrates. Not all nutrition experts believe in this concept of insulin resistance. Yet, because we have a child with this metabolic quirk, we have thoroughly researched this issue, and we believe that for some people there really is a possibility that being over-fat is more the result of producing too much insulin than overeating.
Actually fatness produces more fatness. The more you eat, the higher your blood sugar rises, so the more insulin you secrete. This causes the blood sugar to fall, which makes you hungry again, so you eat more and continue the cycle. Interestingly, a diet with adequate amounts of omega 3 fatty acids (found in fish and flax seed oils) will improve insulin efficiency by helping the body use up carbohydrates and fats for fuel. Imagine - a fat that fights fat.
What about endocrine causes? "Doctor, could it be her thyroid?" is a common question of parents seeking counsel for their overweight adolescent. Generally, but not always, endocrine disorders causing obesity usually also cause children to be short. However, children who are obese, especially from over-nutrition, tend to be taller than average, or at least average height. A short, fat child should always undergo a complete medical evaluation.
"But it's my metabolism." New insights into obesity are showing that for an increasing number of persons, obesity is as much a metabolic problem as much as a behavioral problem. True, many people are overfat because of unhealthy eating behaviors, yet new medical discoveries suggest that problems such as insulin resistance and differences in how people metabolize fat are important contributors to obesity.
Another possible explanation comes from differences between white fat and brown fat. White fat is the fat you see padding the body near the surface. It makes up 90 percent of total body fat. Brown fat, which makes up the other ten percent, is located deeper in the body, primarily within the upper back, around the nape of the neck, the armpits, between the shoulder blades and deep in the chest cavity. Brown fat primarily burns calories, whereas white fat stores calories. Some over-fat people either have less brown fat, or what brown fat they have is not as easily triggered into fat burning, so they tend to store fat rather than burn fat.
The fat cell theory. You may have heard that a person is destined to become lean or fat based on the accumulation of fat cells early in life. The fat cell theory states that during the first two years of life (considered to be one of the critical periods for fat cell development), there is normally an increase in fat cell number. Other spurts in the number of fat cells come in middle childhood, around seven years of age, and again during adolescence. After a person is finished growing and reaches adulthood, the number of fat cells remains constant. The sizes of these cells may change, but they will not decrease in number. Thus someone who is overnourished in childhood (or genetically programmed to grow more fat cells), will have an excess number of fat cells, making it more difficult to control his weight as an adult. While there may be some truth to this fat cell theory (one of the reasons we stress the importance of raising a lean child), new insights suggest that neither the number nor the size of the fat cells is genetically fixed or set for life. It is certainly possible for previously overfat children or adults to become lean for the rest of their lives.
Senior fat. As you age your body tends to gain fat. The good news is that this happens only if you let it. One of the reasons why there is more fat in an older body is that people at retirement age may actually have 25 percent less muscle mass than they did in their twenties, especially males. Since muscle burns calories, a 60-year-old person eating the same number of calories as he did in his twenties is going to get fat. Add to this the fact that an older person may not be as active or as able to exercise. Exercising more and eating more wisely will combat this trend, and often by the time a person is sixty years of age, they are more motivated to watch what they eat in order to avoid disease. Unfortunately, many people don't discover the nutrition-disease connection until they've already gotten a disease. As a tribute to the wisdom of the aging body, most persons in their sixties can simply not "stomach" the quantity of junkfood that make up the diet of most young folk. The key to having an older, yet healthier, body is acquiring nutritional wisdom when you are younger.