Space & Innovation

Couch Potatoes' Brains Can Turn to Mush

Sitting around all day can increase the size of your waistline but could also spell a smaller brain.

Let it never be said that the life of a couch potato is an easy one in spite of all appearances to the contrary. Habitual sofa squatters put their lives on the line for the sake of a few extra hours of R&R, a double feature or two, or a simple season-long marathon of their favorite TV shows.

The cost of all that sitting over the years can spell not only a greater risk of heart disease, diabetes and certain kinds of cancer. Couch potatoes may also have smaller brains.

Failing to maintain adequate levels of physical fitness in middle age can not only shrink your muscles but also potentially reduce brain volume decades later, according to a study released in the journal Neurology.

How the American Diet Has Changed: Photos

For their study, researchers enlisted more than 1,583 middle-aged participants who did not have dementia or heart disease. Those individuals took a simple physical fitness test using a treadmill, while researchers monitored heart rate and blood pressure. The participants also underwent an MRI scan.

Two decades later, the same group repeated the treadmill test and received another MRI scan. The researchers analyzed the results with and without the inclusion of those who had developed heart disease or were taking medication to control blood pressure.

Those who performed worse on the fitness tests were more likely to show smaller brain volume two decades later. Those who fared especially poorly on the physical fitness tests exhibited brain volume reduction equivalent to years of accelerated aging, the researchers found.

Exercising Moms Can Reduce Risks for Newborns

Because the study is observational, the researchers cannot prove causation, but they have demonstrated a direct correlation between poor physical fitness and decreased brain volume.

The Neurology study is hardly the first to show a potential link between exercise and a healthier brain. Earlier this week, researchers in Suomen Akatemia in Finland, who published their findings in the Journal of Physiology, found that aerobic exercise had beneficial effects on brain structure and function.

The hippocampus is a part of the brain important in learning. What the Finnish researchers learned was that running and other forms of sustained aerobic exercise can promote neurogenesis, or neuron growth.

Video: How Exercise Rewires Your Brain

The benefits to the brain were most pronounced as a result of sustained long-distance. High-intensity interval training (HIIT) were minor, and resistance training appeared to offer no brain gains at all.

No one has ever gone to the gym intending to boost the health and size of their brains. But the next time you're on the couch looking for a reason to get up and go, consider that continuing to slack off on the workouts will not only increase your waistline, it might also shrink your brain.

"A characteristic of the American dietary that has persisted throughout years has been its abundance." This sentence is no less true today than when it was

published in the American Journal of Clinical Nutrition in 1959

. That abundance, however, comes with a cost: Americans eat too much. That excess consumption and often poor nutrition has brought with it a multitude of life-changing and often life-threatening diseases and conditions, including obesity, diabetes, heart disease, cancer and more. Although the number of Americans who are overweight or obese has been on a steady climb since the middle of the 20th century,

a recent report by the New York Times suggests

that efforts to abate this health crisis might be gaining ground thanks to a shift in public attitudes. For the first time since the federal government began tracking dietary intake over more than four decades of data collecting, the daily calorie intake of the average American showed a sustained decline. Read on to see how the American diet has changed since the middle of the 20th century.

Americans Falsely Believe Their Diet Is Healthy

While calorie counts have been on the downswing, calorie intake is still far above where it once stood. Americans' daily average caloric intake is over 500 calories higher than it was in 1970, when the average hovered around 2,169 calories per day. What does a more than 20 percent increase in caloric intake mean for the average American? Consider that a pound a fat contains 3,500 calories. Assuming that even a quarter of those calories represent excess energy beyond what's needed for daily maintenance levels, that translates into a pound of stored fat gained every month, or 12 additional pounds per year. Portion sizes have seen a similar increase over time.

According to the U.S. Department of Health & Human Services

, in the last two decades alone, food portions in American restaurants have doubled or in some cases tripled. Portion sizes began increasing in the 1970s and rose sharply in the 1980s. Many food portions greatly exceed USDA and FDA standard servings,

according to a study published in the American Journal of Public Health

. "The largest excess over USDA standards (700 percent) occurred in the cookie category, but cooked pasta, muffins, steaks and bagels exceeded USDA standards by 480 percent, 333 percent, 224 percent and 195 percent, respectively," the study found.

VIDEO: 4 Common Diet Myths Debunked

According to the U.S. Department of Agriculture (PDF)

, between the 1950s and 2000, Americans consumed on average 39 percent more refined sugars. Consumption of corn sweeteners, with high-fructose corn syrup leading the charge, octupled. On average, Americans consume an estimated 156 pounds -- yes, pounds -- of added sugar per capita every year. Excessive sugar intake can lead to all kinds of negative health outcomes, including but not limited to dental problems, obesity, diabetes, liver failure and more. These concerns are what led the

Food and Drug Administration (FDA) recently to propose

a change in food labeling that would recommend the daily intake of calories from added sugars not exceed 10 percent of total consumption. More than 70 percent of U.S. adults get over 10 percent of their daily calories from sugar.

7 Facts About Sugar That May Surprise You

Americans aren't just eating more sugars than they used to; we're also drinking more.

According to the Harvard School of Public Health

, before the 1950s, the standard soft drink size was 6.5 ounces. That decade, manufacturers started selling larger sizes, and by 1960 the 12-ounce can was everywhere. Fast forward 30 years, and 20-ounce bottles are ubiquitous. Today, single-use soft drinks can reach up to 64 ounces and have up to 700 calories. Since the 1970s, sugary drinks have grown from 4 percent of Americans' daily calorie intake to 9 percent. A quarter of Americans get at least 200 calories a day from soft drinks. Teens and children are particularly high consumers, too. Sugar drinks are the top calorie source for teenagers, and are consumed daily by an estimated 91 percent of children.

Does Soda Cause Violence?

Beginning in 1980, when USDA issued the first federal dietary guidelines implicating fats and cholesterol as a major source of Americans' health woes, particularly heart disease, the food industry began shifting formulas in their products that moved away from saturated fat and toward vegetable oils and carbohydrates. Low-fat diets became all the rage, with a bevy of product lines offering low-fat alternatives. What happened after Americans got turned on to low-fat foods? They got even fatter and less healthy. Foods may not have had as much saturated fat, but they made that up with an increase in sugar and refined grains, which kept calorie counts the same. The switch to hydrogenated vegetable oils and margarines also only increased health risks. Heart disease is still the number one killer in the United States, and we also have rising numbers of diabetes and obesity to contend with. In fact, despite numerous studies since the 1990s showing that low fat diets are ineffective at best and harmful at worst, the government continues to recommend a low fat diet.

FDA Bans Trans Fats - More Chemicals to Consider?

Go to the snack aisle of any supermarket or convenience store in the United States, and you'll find a wide array of potential options to satisfy any junk food craving. What do all of these foods have in common? They're all made of refined grains, in addition to other nutritionally deficient ingredients. Refined grains do not offer the same nutritional benefits as whole grains. The process by which refined grains are produced removes fiber, iron, vitamins and other nutrients,

according to the American Heart Association

. Examples of refined grains include white flour, corn flour and white rice. Not only have Americans turned to unhealthier grains for a greater share of their calories; modern wheat is also less nutritious than heritage grain varieties.

Why You Should Probably Stop Eating Wheat

As Americans increasingly eat out at restaurants more and consume more processed foods, salt intake has steadily increased across all age groups. The average American between ages 20 and 74 consumed close to 1,500 mg more sodium per day in 2006 than in 1971,

according to the Institute of Medicine of the National Academies

. The Centers for Disease Control and Prevention (CDC) recommends everyone ages 2 and up consume less than 2,300 mg per day, which is about a teaspoon a day. Some people with certain health risks, such as diabetes or high blood pressure, should limit that further to 1,500 mg per day. Eating too much salt increases water intake in the body, which leads to high blood pressure. Kidneys work overtime to deal with the excess sodium, and the increased blood volume puts a strain on the heart and blood vessels. At worst, a lifetime of a sodium surplus could lead to heart failure or stroke,

according to the Harvard School of Public Health

.

Fast Food Is Less Salty Abroad

In 1929, presidential candidate Herbert Hoover ran under the slogan "a chicken in every pot and a car in every garage." These items might seem common enough today, but Hoover was basically promising what were then considered luxuries to every American household. At the time of Hoover's campaign, "the few chickens raised for meat were sold directly to high-end restaurants, first-class dining cars, and luxury caterers,"

according to the Smithsonian Museum of American History

. Chickens were instead kept for their eggs, which are a valuable source of protein and other nutrients. Egg consumption peaked mid-century, and has been in decline ever since. The overblown connection between cholesterol in eggs and heart disease certainly contributed to Americans turning their back on eggs. But a decline in prices of another protein source, specifically chicken, also contributed to eggs falling out of favor. In the last half of the 20th century, poultry consumption went up more than three-fold, according to USDA data. Red-meat consumption saw a steady decline over the same period, with Americans eating roughly 10 percent fewer pounds per capita every year.

VIDEO: Stop Eating Food: The Soylent Experiment