Exercise, Part 2: The Fountain of Youth and Other Metabolic Effects

Part 1 of the Exercise series focused on how regular physical activity prevented or postponed death. Onward now to other benefits.

Waist Management

Where does the fat go when you lose weight dieting? Chemical reactions convert it to energy, water, and carbon dioxide, which weigh less than the fat. Most of your energy supply is used to fuel basic life-maintaining physiologic processes at rest, referred to as resting or basal metabolism. Basal metabolic rate (BMR) is expressed as calories per kilogram of body weight per hour.

The major determinants of BMR are age, sex, and the body’s relative proportions of muscle and fat. Heredity plays a lesser role. Energy not used for basal metabolism is either stored as fat or converted by the muscles to physical activity. Most of us use about 70 percent of our energy supply for basal metabolism and 30 percent for physical activity. Those who exercise regularly and vigorously may expend 40–60 percent of their calorie intake doing physical activity. Excess energy not used in resting metabolism or physical activity is stored as fat.

Insulin, remember, is the main hormone converting that excess energy into fat; and carbohydrates are the major cause of insulin release by the pancreas.

To some extent, overweight and obesity result from an imbalance between energy intake (food) and expenditure (exercise and basal metabolism). Excessive carbohydrate consumption in particular drives the imbalance towards overweight, via insulin’s fat-storing properties.

In terms of losing weight, the most important metabolic effect of exercise is that it turns fat into weightless energy. We see that weekly on TV’s “Biggest Loser” show; participants exercise a huge amount. Please be aware that conditions set up for the show are totally unrealistic for the vast majority of people.

Physical activity alone as a weight-loss method isn’t very effective. But there are several other reasons to recommend exercise to those wishing to lose weight. Exercise counteracts the decrease in basal metabolic rate seen with calorie-restricted diets. In some folks, exercise temporarily reduces appetite (but others note the opposite effect). While caloric restriction during dieting can diminish your sense of energy and vitality, exercise typically does the opposite. Many dieters, especially those on low-calorie poorly designed diets, lose lean tissue (such as muscle and water) in addition to fat. This isn’t desirable over the long run. Exercise counteracts the tendency to lose muscle mass while nevertheless modestly facilitating fat loss.

How much does exercise contribute to most successful weight-loss efforts? Only about 10 percent on average. The other 90 percent is from food restriction.

Fountain of Youth

Regular exercise is a demonstrable “fountain of youth.” Peak aerobic power (or fitness) naturally diminishes by 50 percent between young adulthood and age 65. In other words, as age advances even a light physical task becomes fatiguing if it is sustained over time. By the age of 75 or 80, many of us depend on others for help with the ordinary tasks of daily living, such as housecleaning and grocery shopping. Regular exercise increases fitness (aerobic power) by 15–20 percent in middle-aged and older men and women, the equivalent of a 10–20 year reduction in biological age! This prolongation of self-sufficiency improves quality of life.

Heart Health

Exercise helps control multiple cardiac (heart attack) risk factors: obesity, high cholesterol, elevated blood pressure, high triglycerides, and diabetes. Regular aerobic activity tends to lower LDL cholesterol, the “bad cholesterol.” Jogging 10 or 12 miles per week, or the equivalent amount of other exercise, increases HDL cholesterol (“good cholesterol”) substantially. Exercise increases heart muscle efficiency and blood flow to the heart. For the person who has already had a heart attack, regular physical activity decreases the incidence of fatal recurrence by 20–30 percent and adds an extra two or three years of life, on average.

Effect on Diabetes

Eighty-five percent of type 2 diabetics are overweight or obese. It’s not just a random association. Obesity contributes heavily to most cases of type 2 diabetes, particularly in those predisposed by heredity. Insulin is the key that allows bloodstream sugar (glucose) into cells for utilization as energy, thus keeping blood sugar from reaching dangerously high levels. Overweight bodies produce plenty of insulin, often more than average. The problem in overweight diabetics is that the cells are no longer sensitive to insulin’s effect. Weight loss and exercise independently return insulin sensitivity towards normal. Many diabetics can improve their condition through sensible exercise and weight management.

Miscellaneous Benefits

In case you need more reasons to start or keep exercising, consider the following additional benefits: 1) enhanced immune function, 2) stronger bones, 3) preservation and improvement of flexibility, 4) lower blood pressure by 8–10 points, 5) diminished premenstrual bloating, breast tenderness, and mood changes, 6) reduced incidence of dementia, 7) less trouble with constipation, 7) better ability to handle stress, 8) less trouble with insomnia, 9) improved self-esteem, 10) enhanced sense of well-being, with less anxiety and depression, 11) higher perceived level of energy, and 12) prevention of weight regain.

People who lose fat weight but regain it cite lack of exercise as one explanation. One scientific study by S. Kayman and associates looked at people who dropped 20 percent or more of their total weight, and the role of exercise in maintaining that loss. Two years after the initial weight loss, 90 percent of the successful loss-maintainers reported exercising regularly. Of those who regained their weight, only 34 percent were exercising.

 Part 3 of this series gets into specific exercise recommendations.

Steve Parker, M.D.


Filed under Exercise, Weight Loss, Weight Regain

12 responses to “Exercise, Part 2: The Fountain of Youth and Other Metabolic Effects

  1. Seth W.

    Carbohydrate isn’t the only macronutrient to cause the pancreas to release insulin, as protein as a pretty marked affect as well. Which leads me to my next point, which is that even though insulin goes up with either carbs or protein (which insulin shoots up even more with protein consumption) that release in insulin also interacts with leptin to cause satiety.

    Bottom line: there are plenty of people that I know who don’t give a crap about the white pasta and other refined foods. Sure they might not be ripped as all hell, but they aren’t overweight either. It seems that people who eat refined foods (including other fast foods such as McDonalds, Taco Bell and such) have decent weights, as long as they aren’t either stuffing themselves or drinking one-liter cokes alongside their meal.

  2. Hi, Seth. My understanding is that, gram for gram, carbohydrates lead to a significantly greater insulin release than do proteins. Furthermore, the presence of dietary fat also reduces the insulin spike induced by either carbs or proteins. Most animal-based protein sources are accompanied by significant amounts of fat. On the other hand, it’s easier to find low-fat refined carbohydrates, such as table sugar.

    I agree completely that many people can eat fast food and refined carbs without becoming overweight. They can even have ripped bodies. Remember, however, that 65% of American adults are either overweight or obese, for whatever reason.

  3. Seth W.


    Isn’t it also true that levels of insulin doesn’t necessarily correlate with increased levels of blood glucose? Or at least that they’re somewhat separate concepts?

  4. It’s hard to make firm generalizations about insulin levels and their relationship to blood sugar levels because there are lots of variables at play.

    Let’s consider young, healthy, non-diabetic, non-prediabetic adults. As blood sugar starts to rise after a meal containing carbs or proteins, the pancreas secretes insulin at a higher rate in order to lower the blood sugar level, with the ultimate goal of utilizing the energy stored in the glucose molecule. Whether the higher insulin secretion rate will be detected with a simple insulin blood level depends on the body’s degree of insulin sensitivity/resistance, and the sensitivity of the lab assay used to measure serum insulin levels. Scientists have methods to actually measure the insulin secretion rate.

    If we look at other groups of people, the measured insulin level will depend on the presence of diabetes, prediabetes, type of diabetes, overweight, obesity, lean body mass, age, finess level, composition of the diet, etc. For instance, early on in the disease process, type 2 diabetics tend to have high blood sugars and high insulin levels (high insulin levels to overcome insulin resistance). Later on, the pancrease beta cells may become exhausted or “burned out,” with lower insulin levels as blood sugars continue to rise.

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