Creating, collecting, and sharing thoughts and ideas. And learning along the way.
This week marks the start of the annual eat-too-much and move-too-little holiday season, with its attendant declining health and surging regrets. But a well-timed new study suggests that a daily bout of exercise should erase or lessen many of the injurious effects, even if you otherwise lounge all day on the couch and load up on pie.
To undertake this valuable experiment, which was published online in The Journal of Physiology, scientists at the University of Bath in England rounded up a group of 26 healthy young men. All exercised regularly. None were obese. Baseline health assessments, including biopsies of fat tissue, confirmed that each had normal metabolisms and blood sugar control, with no symptoms of incipient diabetes.
The scientists then asked their volunteers to impair their laudable health by doing a lot of sitting and gorging themselves.
Energy surplus is the technical name for those occasions when people consume more energy, in the form of calories, than they burn. If unchecked, energy surplus contributes, as we all know, to a variety of poor health outcomes, including insulin resistance — often the first step toward diabetes — and other metabolic problems.
Overeating and inactivity can each, on its own, produce an energy surplus. Together, their ill effects are exacerbated, often in a very short period of time. Earlier studies have found that even a few days of inactivity and overeating spark detrimental changes in previously healthy bodies.
Some of these experiments have also concluded that exercise blunts the ill effects of these behaviors, in large part, it has been assumed, by reducing the energy surplus. It burns some of the excess calories. But a few scientists have suspected that exercise might do more; it might have physiological effects that extend beyond just incinerating surplus energy.
To test that possibility, of course, it would be necessary to maintain an energy surplus, even with exercise. So that is what the University of Bath researchers decided to do.
Their method was simple. They randomly divided their volunteers into two groups, one of which was assigned to run every day at a moderately intense pace on a treadmill for 45 minutes. The other group did not exercise.
Meanwhile, the men in both groups were told to generally stop moving so much, decreasing the number of steps that they took each day from more than 10,000 on average to fewer than 4,000, as gauged by pedometers. The exercising group’s treadmill workouts were not included in their step counts. Except when they were running, they were as inactive as the other group.
Both groups also were directed to start substantially overeating. The group that was not exercising increased their daily caloric intake by 50 percent, compared with what it had been before, while the exercising group consumed almost 75 percent more calories than previously, with the additional 25 percent replacing the energy burned during training.
Over all, the two groups’ net daily energy surplus was the same.
The experiment continued for seven days. Then both groups returned to the lab for additional testing, including new insulin measurements and another biopsy of fat tissue.
The results were striking. After only a week, the young men who had not exercised displayed a significant and unhealthy decline in their blood sugar control, and, equally worrying, their biopsied fat cells seemed to have developed a malicious streak. Those cells, examined using sophisticated genetic testing techniques, were now overexpressing various genes that may contribute to unhealthy metabolic changes and underexpressing other genes potentially important for a well-functioning metabolism.
But the volunteers who had exercised once a day, despite comparable energy surpluses, were not similarly afflicted. Their blood sugar control remained robust, and their fat cells exhibited far fewer of the potentially undesirable alterations in gene expression than among the sedentary men.
“Exercise seemed to completely cancel out many of the changes induced by overfeeding and reduced activity,” said Dylan Thompson, a professor of health sciences at the University of Bath and senior author of the study. And where it did not countermand the impacts, he continued, it “softened” them, leaving the exercise group “better off than the nonexercise group,” despite engaging in equivalently insalubrious behavior.
From a scientific standpoint, this finding intimates that the metabolic effects of overeating and inactivity are multifaceted, Dr. Thompson said, with an energy surplus sparking genetic as well as other physiological changes. But just how exercise countermands those effects is impossible to say based on the new experiment, he added. Differences in how each group’s metabolism utilized fats and carbohydrates could play a role, he said, as could the release of certain molecules from exercising muscles, which only occurred among the men who ran.
Of more pressing interest, though, is the study’s practical message that “if you are facing a period of overconsumption and inactivity” — also known as the holidays — “a daily bout of exercise will prevent many of the negative changes, at least in the short term,” Dr. Thompson said. Of course, his study involved young, fit men and a relatively prolonged period of exercise. But the findings likely apply, he said, to other groups, like older adults and women, and perhaps to lesser amounts of training. That’s a possibility worth embracing as the pie servings accumulate.
THE solution to one of America’s most vexing problems — our soaring rates of obesity and diet-related diseases — may have its roots in early childhood, and even in utero.
“What’s really interesting about children is, the preferences they form during the first years of life actually predict what they’ll eat later,” said Julie Mennella, a biopsychologist and researcher at the Monell Center. “Dietary patterns track from early to later childhood but once they are formed, once they get older, it’s really difficult to change — witness how hard it is to change the adult. You can, but it’s just harder. Where you start, is where you end up.”
This may have profound implications for the future health of Americans. With some 70 percent of the United States population now overweight or obese and chronic diseases skyrocketing, many parents who are eating a diet high in processed, refined foods are feeding their babies as they feed themselves, and could be setting their children up for a lifetime of preferences for a narrow range of flavors.
The Monell researchers have identified several sensitive periods for taste preference development. One is before three and a half months of age, which makes what the mother eats while pregnant and breast-feeding so important. “It’s our fundamental belief that during evolution, we as humans are exposed to flavors both in utero and via mother’s milk that are signals of things that will be in our diets as we grow up and learn about what flavors are acceptable based on those experiences,” said Gary Beauchamp, the director of the Monell Center. “Infants exposed to a variety of flavors in infancy are more willing to accept a variety of flavors, including flavors that are associated with various vegetables and so forth and that might lead to a more healthy eating style later on.”
There is another reason these exposures have a lifelong impact, he said: “This early exposure leads to an imprinting-like phenomenon such that those flavors are not only preferred but they take on an emotional attachment.”
This puts babies fed formula at a disadvantage because the flavors in packaged formula never change. But according to Ms. Mennella, the opportunity to expose those babies to a range of flavors is not lost. “Just because you’re formula-fed, it’s not hopeless,” she said. “Babies learn through repeated exposure, so the more varied the diet, the more likely they’ll be to accept a novel food.”
Another recent study conducted at the FoodPlus research center at the University of Adelaide in South Australia found that exposure to a maternal junk food diet (defined in the study as any food that was energy dense, highly palatable and had a high fat content) results in children with a preference for these same foods. In a rodent model, the study found that being exposed to too much junk food in utero and through breast milk leads offspring to develop a reward pathway in the brain that is less sensitive than normal. Mothers who were fed foods like Froot Loops, Cheetos and Nutella during pregnancy had offspring that showed increased expression of the gene for an opioid receptor, which resulted in a desensitization to sweet and fatty foods. “The best way to think about how having a desensitized reward pathway would affect you is to use the analogy of somebody who is addicted to drugs,” Jessica R. Gugusheff, a Ph.D. candidate at FoodPlus and the lead author of the study, wrote in an email. “When someone is addicted to drugs they become less sensitive to the effects of that drug, so they have to increase the dose to get the same high,” she wrote. “In a similar way, by having a desensitized reward pathway, offspring exposed to junk food before birth have to eat more junk food to get the same good feelings.”
Ms. Mennella at Monell has also done research on reward pathways for sweetness and has found that sweet flavors have an analgesic effect on babies and children such that babies will cry less and children will leave their hand in a cold water bath for longer periods with sweet flavors in their mouths. Ms. Mennella has also found that in obese children, while the level of sweet they prefer is the same as that of normal-weight children, sweet flavors are not as effective as an analgesic. “I hypothesized maybe it’s because of some disruption in the opioid system, so maybe they need more sweet to get the same effect,” she said.
These research studies call into question the ethics of marketing poor-quality foods to children as well as the marketing of infant formula.
In the United States, according to the Centers for Disease Control and Prevention, about 15 percent of mothers breast-feed exclusively for six months, with rates significantly lower for African-American mothers. The American Academy of Pediatrics recommends that women breast-feed exclusively for at least six months and then continue some breast-feeding as they introduce solid foods for the next six months. The World Health Organization recommends breast-feeding up to 2 years of age or beyond.
But infant formula is a booming billion-dollar industry with three companies controlling almost 98 percent of the market: Mead Johnson, maker of Enfamil, Abbott, manufacturer of Similac, and Nestlé (now Gerber), maker of Good Start.
Functional foods, or foods that allegedly deliver nutritional benefit beyond what is available in natural foods, are a food industry creation to convince consumers that their products are superior to, or can replace, natural, whole foods. Globally, infant formula is the fastest growing functional food; the market is on track to grow by nearly $5 billion in 2013 alone.
But formula is only part of the problem since breast-fed babies of mothers eating too many refined and processed foods are also at risk. Claims by the food industry that personal responsibility, exercising more, and eating less are the solutions to obesity and diet-related disease are turned on their head with these studies. If babies are developing food preferences in utero and before 2 or 3 years of age through no fault of their own, how can we then blame them when they become obese children and adults?
If we hope to reverse the tide on obesity and diet-related disease in America, regulating processed food products and infant formula, and creating clear warning labels to deter parents from feeding their children potentially harmful foods may be our best shot. Let’s make sure future generations have the best chance to become healthy adults.
