Getting Fit: the Science behind Exercise

In this Article (Index)

• Lower Heart disease risk
• Health benefits of physical activity
• improve memory and avoid dementia
• treats depression
• live longer
• Telomeres
• Exercise inhibits inflammation
• Exercise Reduces Mortality Risk
• Exercise helps beat abdominal fat and metabolic syndrome
• Weight loss
• Physical Activity Guidelines

Heart disease risk and exercise

Keeping active is a great way to live better and longer. But, what is the exact link between exercising and cardiovascular disease (CVD) risk? Does exercising more reduce the risk of having a heart failure? Let's see what science has to say about it:

The American Heart Association (2015) (1) is quite clear about the benefits of physical activity:

"Doubling or quadrupling the minimum federally recommended levels of physical activity lowered the risk of developing heart failure by 20 percent and 35 percent, respectively."

The study also reports that the more that you exercise, the lower the risk of heart failure.

This conclusion is based on data from cclinical studies in the US and Europe involving more than 370,000 subjects over a 15-year follow-up.

However, another study (Batacan, 2015) (2) looked into the effects of light intensity physical activity on cardiovascular disease reviewed the data published between 1970 and 2015 and found that light-intensity physical activity "did not improve CVD risk factors... in healthy individuals." However, it did improve blood pressure in "physically inactive populations with a medical condition," like people with high blood pressure.

The authors believed that this strange outcome (you would expect a lower CVD risk in people who exercised) was due to the low-quality of the studies that didn't monitor other effects such as food intake, and the low doses of light-exercise used in them.

Don't overdo it

Sedentarism can hurt your heart and training too much can also damage it. James O'Keefe and his team (2012) (3) reported that people should exercise within the limits laid down by the Physical Activity Guidelines (more on these guidelines further down) because high-intensity endurance training can increase the risk of "adverse cardiovascular events" (and musculoskeletal injuries too!)

Those who train and compete in extreme endurance events (ironman, triathlon, marathons, ultramarathons, and very long-distance bike races) suffer small damage which goes unnoticed, yet after years of repetitive injury can eventually damage parts of the heart, and be the cause of arrhythmias and calcification, and wall-stiffening to arteries among other conditions.

The team reported that "Veteran endurance athletes in sports such as marathon or ultramarathon running or professional cycling have been noted to have a 5-fold increase in the prevalence of atrial fibrillation."

Some unexpected health benefits of physical activity

Apart from contributing to shedding fat and maintaining a healthy weight and ward off heart disease, exercise also helps your health in other ways by preventing dementia, depression, and extending your lifespan. Here's what science has to say about it:

Exercising can help improve memory and avoid dementia

Alzheimer's disease appears in a part of the brain known as the "hippocampus" (Learn more about the hippocampus) which has an important role in memory-processing and learning.

That is why the onset of the disease causes severe memory loss. The hippocampus shrinks as you age, but a controlled trial with 120 older adults (Erickson, 2011) (4) found that very fit adults had larger hippocampal volume, and that "exercise training increased hippocampal volume by 2%, effectively reversing age-related loss in volume by 1 to 2 years."

Exercise is a good treatment for depression

James Blumenthal and his team (2012) (5) report that even moderate levels of "exercise [are] an effective treatment for depression, improving depressive symptoms to a comparable extent as pharmacotherapy and psychotherapy."

Active people are less likely to become depressed. Aerobic and Resistance Training are equally effective, and "any exercise is better than no exercise."

A review of clinical studies Karamacoska (2023) confirmed these findings, reporting that: "Exercise improved global cognition, executive function [and was] linked with improved global cognition, memory, and executive function" (17).

You may live longer if you exercise

Longer telomeres equal a longer lifespan

James H. O'Keefe (2012) (3) reported that "People who exercise regularly have... a mean life expectancy that is 7 years longer than that of their physically inactive contemporaries." But what is the exact mechanism?

Telomeres

Apparently, telomeres are involved in this life-extending benefit of exercise.

Telomeres are chunks of nucleoproteins that act as caps at the tips of each strand of DNA inside your chromosomes. They protect them (keeping them from sticking to each other). They are like those plastic tips at the ends of your shoelaces.

Larry Tucker (2017) (6) studied 5,823 adults from the National Health and Nutrition Examination Survey (NHANES 1999-2002) comparing their telomere lengths to that of a standard reference DNA. As their level of physical activity was known, it was easy to check if there was any link between telomere length and exercise.

The study found that as you age, telomeres become shorter by 15.6 base pairs each year that passes and this causes cell deterioration and aging.

But those who engaged in routine physical activity had longer telomere length. Adults with high physical activity levels had telomeres that were longer than those of less active ones.

The results were striking, in favor of the highly active people:

• 140 base pairs longer than those of sedentary adults.
• 137 base pairs longer than those of low activity adults.
• 111 base pairs longer than those of moderate activity adults.

This translates into a "biologic aging advantage of 9 years (140 base pairs ÷ 15.6) over Sedentary adults," 8.8 years vs. Low activity adults, and 7.1 years over Moderately active adults.

Why does this happen? Maybe the antioxidant properties of a healthier lifestyle (less body fat means less oxidative stress for the body) help conserve telomere length.

Exercise inhibits inflammation

Stoyan Dimitrova, Elaine Hultenga, and Suzi Honga, (2017) (7) investigated how regular exercise exerts anti-inflammatory effects by studying how 20-minute periods of moderate exercise-induced the release of catecholamine, which in turn has an anti-inflammatory effect.

Their results suggest that this type of exercise "may protect against chronic conditions with low-grade inflammation."

Catecholamines are also neurotransmitters that affect the immune response, so exercise may also impact positively on immunity.

Exercise Reduces Mortality Risk

A study (8) involving 334,161 European men and women followed-up for at least 12.4 years revealed that "The higher risk of death resulting from excess adiposity may be attenuated by physical activity."

The all-cause mortality in moderately inactive individuals was 16 to 30% lower than that of "inactive individuals." So even small increases in levels of physical activity can go a long way in reducing mortality.

The activity effect on mortality was two times that of avoiding obesity while being physically inactive had the same risk as having a high waist circumference.

Learn why Waist Size Matters when it comes to your health.

Exercise helps beat abdominal fat and metabolic syndrome

Metabolic Syndrome

Metabolic syndrome affects 1 out of every 5 adults around the world. It is defined as a combination of at least three of the following risk factors:

1. Abdominal obesity (high visceral fat).
2. High blood pressure.
3. High levels of triglycerides in your blood, low levels of "good" cholesterol (high-density lipoprotein or HDL), and insulin resistance.

Abdominal fat is the main culprit as it provokes all the other factors involved in metabolic syndrome.

Paley and Johnson (2018) (9) reported that "there is moderate evidence supporting the use of programmes of exercise to reverse metabolic syndrome."

They also cited a study showing that aerobic and resistance training and high resistance-moderate endurance training helped reduce visceral fat. Adding that the loss of this type of fatty tissue was more important than weight loss.

Our page on the "Dangers of Abdominal Fat" explains the health risks associated with a fat midsection:

Yes, aerobic exercise causes weight loss

Study after study shows that exercise helps overweight and obese subjects lose weight. These trials include different types of physical activity, but all show that being active helps lose fat and weight. Below we summarize some of these studies:

• Exercise that burned 400 calories per session, 5 days a week for 10 months led to a 4.3% loss of body mass (8.6 lbs), those who burned 600 calories per session lost 5.7% of their body weight (11.5 lbs), the sedentary control group gained 1.1 lbs weight (0.5%) (10).
• Resistance training (RT) led to a loss of body mass, fat mass, reduced total cholesterol, triglycerides, and "Bad" LDL cholesterol. It also reduced insulin levels more than endurance training (8).
• Sedentary obese, or overweight, non-diabetic adults lost more weight and fat mass with aerobic training than with resistance training (though RT led to an increase in muscle mass) (11).
• Obese and overweight women: diet alone led to more weight loss than exercise alone, but when they combined diet plus exercise, they experienced even greater fat loss and changes in body weight and composition (12).

The amount and intensity of physical activity is the key

Damon Swift and his team (2014) (13) reported that following aerobic exercise training programs in line with the public health guidelines (See guidelines below) provoked a modest weight loss (4.4 lbs or 2 kg) that may be below the expectations of many of those who engage in physical activity to lose weight.

However, Swift pointed out that "numerous health benefits occur from Physical Activity programs in the absence of weight loss," so even if you don't lose weight, that doesn't mean that you aren't benefiting from your exercise.

For instance, to prevent weight gain, you should do 150-250 minutes per week of moderate to vigorous physical activity burning around 1,200 to 2,000 calories weekly.

Those who reap the most benefits from exercise regardless of weight loss are the overweight and obese individuals at risk for cardiovascular diseases.

Exercise will prevent you from regaining lost weight

Finally, adhering to an exercise training program over the long-term plays a major role in keeping the lost pounds off, and not regaining them.

A study involving a group that dieted in combination with aerobic exercise training lost the same weight as another group that dieted and did the minimum physical activity suggested by the guidelines (+17 lbs after 16 weeks - 8 kg).

But, one year later, those who were most active lost an extra 4.2 lb (1.9kg) while the other group regained weight (10.8 lb or 4.9 kg).

Your body will try to compensate for the energy burned during exercise

The effect of additional exercise was also reported in a recent study by Kyle Flack and his team (2018) (14) that looked into the effect of "extra" exercise and weight loss.

To do so they organized two groups of sedentary overweight to obese men and women; they were to exercise 5 days per week. One group was to burn 300 calories per exercise session, and the other one 600 calories per session.

After 12 weeks they were tested, the 3,000 calories per week group lost weight and body fat while the 1,500 calories per week group did not lose weight or fat.

The study found that somehow the bodies of the participants tried to "compensate" for the extra energy expenditure either by eating more or moving less throughout the day. But the "compensatory effect" was almost the same in both groups (around 1,000 calories) which more or less compensated the energy expended by the least active group, so they didn't lose weight.

The 3,000 calories per week group on the other hand, only compensated 1,000 calories, so their weekly deficit was 2,000 calories, and that is what led to their weight loss (they burned more fat to cover this deficit).

The authors concluded that compensation is not proportionate to energy expenditure meaning that you need to exercise more vigorously to shed pounds.

Physical Activity Guidelines

The Physical Activity Guidelines for Americans (15) defined by the U.S. Department of Health and Human Services lays down the recommended amount and type of physical activity needed to maintain health:

Guidelines for Adults 18 to 64 years old

• Any physical activity (PA) is better than none. Avoid inactivity. Any amount of PA will provide health benefits.
• For "substantial" health benefits: Do at least 150 minutes per week (2 hours and 30 minutes) of moderate-intensity activity or 75 minutes (1 hour and 15 minutes) of vigorous-intensity aerobic physical activity each week. Or a combination of both.
• Aerobic activity should last at least 10 minutes and be spread out throughout the week.
• For even more health benefits increase the moderate-intensity aerobic activity to 5 hours per week or the vigorous-intensity to 150 minutes weekly.
• You should also include muscle-strengthening activities involving all major muscle groups on 2 or more days a week.

Guidelines for Older Adults: 65 years and older

• Try to follow the adult guidelines above, if you can't then try to keep as physically active as possible.
• Exercise to maintain and improve balance -to avoid the risk of falling.
• Your level of physical activity (PA) should be in line with your level of fitness.
• Those suffering from chronic health conditions should understand whether and how their conditions affect their ability to do regular PA safely.

Some definitions

• Moderate-intensity physical activity is an aerobic activity that increases your heart rate and breathing somewhat. So it is a 5 or 6 on a 0 to 10 scale.
  Examples: Brisk walking, swimming, cycling on level terrain, or dancing. You can maintain a conversation during moderate PA.
• Vigorous-intensity physical activity is an aerobic activity that greatly increases your heart rate and breathing. It is a 7 or 8 on a 0 to 10 scale.
  Examples: singles tennis, cycling uphill, jogging, swimming continuous laps. You will find it hard to keep up a conversation.
• Muscle-strengthening activity: PA that builds muscle power, mass, and endurance. It includes strength training, resistance training, muscular strength, and endurance exercises.