Archive for Basics of Weight Loss

Factors That Affect Body Weight 9

Physical activity
A low level of physical activity is one of the most important factors in the high and rising rate of obesity in the United States. People are simply not getting enough exercise.

Becoming physically active can have a tremendous impact on your total daily energy expenditure. For example, a sedentary person burns just a few hundred calories above his or her resting metabolic rate while going about daily activities (performing household chores or walking to the mailbox, for example). (see our section on Metabolism for more information).

Someone who exercises regularly at a moderate pace doing light gardening or yard work, walking, or dancing can burn an additional 150 calories per half hour—and build muscle mass.

Exercises that build strength also raise the resting metabolic rate because muscle requires more energy for maintenance.

Factors That Affect Body Weight 8

Dietary intake continued
To point to overeating as the cause of obesity is overly simplistic, however. It does not explain why one 125 pound woman can eat 1,800 calories a day and not gain weight, while another woman at the same weight struggles to avoid gaining weight on 1,200 calories a day.

This difference occurs because numerous other factors contribute to weight gain, including resting metabolic rate and physical activity, as we have discussed.

Nevertheless, obese people must be consuming more calories than required by their individual makeups and activity levels. Otherwise they would not store excess body fat.

Thus, if you’re overweight, you must reduce your calorie intake to lose weight successfully, and then moderate your calorie intake in order to keep it off long term.

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Lifestyle Factors That CAN Be Changed For Weight Loss

The following factors affect weight and ARE under your control. So if you are worried about your weight, even small changes in these areas can add up to big results.

Dietary intake
Eating more calories than you expend is an important cause of obesity.As we have said, gaining one pound requires only 2000 excess calories, but losing the same pound means you have to burn 3000.

Once you realize this, you might never look at your chocolate cake or ice cream the same way again…

The plain fact is, you ARE what you eat. Regardless of your genetic predisposition to obesity or your resting metabolic rate, you can’t gain weight without consuming more calories than you burn.

Sadly, even small excesses in calorie intake can add pounds over the long term. For example, a person who overeats by just 25 calories a day will consume 9,125 excess calories over the course of a year and thus gain weight, unless they make up for it with more exercise. A woman weighing 125 lbs who starts this pattern at age 20 would weigh 200 lbs by the time she was aged 50.

Factors That Affect Body Weight 6


Metabolism continued

Set point theory
According to this theory, you have a predetermined weight and level of body fat—called a set point—that your body wants to maintain.

This body fat level is determined by genetics, just like your height. Exactly how the body controls its fat stores is unknown, but the regulatory mechanism, sometimes called the adipostat, is located in the brain.

The adipostat monitors the body’s fat stores, possibly through the actions of the hormone leptin, and works to maintain the set point by adjusting appetite, physical activity, and resting metabolic rate to conserve or expend energy.

Thus, eating and physical activity may be subtly controlled by the set point mechanism.

For more information on Metabolism, visit the Metabolism section of this website.

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Metabolism continued

So it is important to remember that due to metabolism, weight loss or gain  is NOT a one-to-one ratio, as we thought. If a gained pound is equal to 2000 extra calories, a lost pound is equal to 3000.

This is bad news for all of us who thought we were not going to suffer the consquences of that little microwave chocolate cake that comes in at about 500 calories, or the fast food meal at over 700.  Or the coffee house beverage that comes in at a whopping 750, with MORE saturated fat than the fast food meal!

So successful weight loss is not just about watching what you eat. Your metabolism does have a part to play. However, as we will be discussing later, it is also all about making SMART choices about what you choose to spend your ‘calorie allowance’ on.

Factors That Affect Body Weight 4

Metabolism continued

Whether or not obese people have an abnormally slow metabolism is controversial. In fact, it takes more energy to maintain a greater body mass.

For example, a person who weighs 200 lbs has a higher resting metabolic rate than someone who weighs 150 lbs. In addition, the 200-lb person expends more calories than the 150-lb person for any given physical activity.

But even when people of the same height, weight, age, gender, and muscle mass are compared, their resting metabolic rates vary by 20% or more.

This means that if you are predicted to use 1,200 calories through your resting metabolic rate, you may actually use anywhere from 1,080–1,320 calories.

This variability explains in part why two people who weigh the same may require different amounts of calories to maintain, lose, or gain weight.

It’s important to remember that whatever your resting metabolic rate, if you consume more calories than you expend, those extra calories will be stored primarily as fat.

This will happen regardless of whether the extra calories come from fats, carbohydrates, or proteins (although dietary fat is converted into body fat more efficiently than dietary proteins or carbohydrates).

Factors That Affect Body Weight 3

Your Metabolism
This is the process that extracts and utilizes energy (measured in calories) from food. Even at rest, energy is needed for many functions, such as: the beating of your heart, breathing, and cell growth and repair.

The amount of energy used for these basic functions while you are at rest is known as your resting metabolic rate, which accounts for about 70% of your body’s use of energy each day.

Your resting metabolic rate is affected by your weight, age, level of physical activity, and the amount of muscle in your body. Having more muscle increases your metabolic rate, since muscle utilizes more energy than fat, even at rest. Your resting metabolic rate is also in part genetically determined. (see the Metabolism section of this website for more information on metabolism)

The act of eating also uses up energy, because energy is needed to digest food, absorb nutrients, and store excess calories as body fat.

This process—called thermogenesis—accounts for 10 to 15% of the body’s total daily energy expenditure. Some research suggests that obese people require slightly less energy for thermogenesis than normal-weight people, and thus more of the calories they eat are stored as fat rather than used to process food.

Factors That Affect Body Weight 2

Genetic Factors Continued
A number of genes are responsible for regulating body weight.

More than a decade ago, researchers at Rockefeller University discovered that mutations in a gene—called the obesity (ob) gene— prevented a strain of mice from producing leptin.

Leptin is a hormone normally manufactured by fat cells, and released into the blood to inform the brain about the body’s level of fat stores.

When this communication system works properly, the brain responds to leptin by reducing appetite and speeding up metabolism to maintain a normal level of body fat.

Because the mice with the mutated ob gene did not produce leptin, their brains continually sent messages to the rest of the body to eat and store fat, and the mice became obese.

However, when leptin was injected into the obese mice, they quickly lost weight through a combination of decreased food intake and increased activity.

Since this discovery, however, researchers have found that administering leptin to obese people rarely reduces weight, because their blood leptin levels are already high and/or their bodies are resistant to the effects of leptin.

Still, unraveling the link between leptin (and other substances released by fat cells) and weight control may lead to the development of more effective drugs for weight loss.

Factors That Affect Body Weight 1

Controllable factors—for example, a high-calorie diet, emotional responses to food (such as eating when anxious or bored), too large portion sizes, automatic eating, and a lack of exercise—play a crucial role in the development of obesity.

Yet research confirms that more is involved in losing weight and keeping it off than just a lack of willpower or a sedentary lifestyle.

Factors That Cannot Be Changed
Although these factors are beyond your control, their impact on your weight can be modified by changing your diet and increasing your level of physical activity.

Heredity
Studies show that 80% of children born to two obese parents will themselves become obese, compared with 14% of children born to normal-weight parents.

Research on identical twins shows similarly high rates of inheritance factor when it comes to weight.

However, studies comparing the weights of adoptees with the weights of their biological and adopted parents indicate that genetic factors are responsible for only about a third of the difference in weight.

Heredity seems to influence the number of fat cells in the body, how much and where fat is stored, and how much energy the body uses at rest (metabolism).

In addition, childhood obesity tends to translate into adult obesity.

About 80% of obese children become obese adults (although only about 20% of all obese adults were obese as children).

Watching Your Weight

Good nutritional habits aren’t just important for preventing diseases, they can also help you watch your weight.

Rates of overweight and obesity are higher than ever in the United States, alarmingly so.

According to the Centers for Disease Control and Prevention (CDC), more than six in 10 American adults are overweight or obese—and most adults are about 25 pounds heavier than people were in the 1960s.

To make matters worse, more than half of all overweight people actually think they’re at a healthy weight, according to a recent Associated Press poll.

In theory, weight management to stay at a healthy weight is a simple matter of balancing energy intake (the calories supplied by food) with energy output (the calories expended by physical activity, the digestion of food, and the functioning of your body).

To lose weight, you need to expend more energy than you take in. In practice, however, the task is not that simple. While the basic principle of energy balance remains true, several factors—genetic, metabolic, and environmental—can affect how much you eat and how your body uses and stores energy.

Even if the genetic and metabolic components involved in weight management are mostly beyond your control, the good news is that environmental factors ARE controllable and can have a significant impact. By manipulating these controllable factors to your advantage, you can successfully lose weight and keep it off.

In this series, we will be talking about the factors that contribute to your weight loss and gain, and what you can do about them, for effective weight management, or even weight loss.