Here’s another theory that may simultaneously be true. Many people believe that exercising gives them permission to eat more than they are actually hungry for. They never allow themselves to experience the more important weight-lowering benefits, such as reduced appetite (relative to the increased energy spent) and increased sensitivity to hunger/fullness signals. Because they do not respond to their body signals, the improvements stimulated by exercise do not have a noticeable effect on eating habits, and they may even eat more to compensate.
66
In support of these theories, one research study monitored large women on an exercise program.
56
They noticed that as the women participated in the exercise program, their leptin output increased and their appetites correspondingly decreased. Despite this decrease in appetite, however, their food intake didn’t change. In other words, appetite was reduced—evidence that their bodies were trying to support them in weight loss—but they weren’t paying attention to it, with the result that their increased exercise habits never showed on the scale.
Perhaps individuals who exercise regularly while simultaneously taking advantage of their heightened sensitivity to hunger and fullness signals will have better success lowering their weight through exercise, if that is what their bodies are meant to do. In other words, exercise may only be a weight-lowering technique when coupled with dumping the diet mentality and replacing it with internally regulated eating habits.
While it is unclear whether being regularly active reduces one’s setpoint, there is no doubt that increased activity, in addition to being fun, is the single most important thing you can do to improve your health and well-being. Active people are much healthier than sedentary ones,
regardless of weight
.
67
Exercise can cure, prevent, or minimize most of the major chronic diseases and disturbances, including diabetes, insulin resistance, hypertension, high cholesterol levels, cancer, digestive disorders, circulatory disorders, etc.
Also important, being active can help you feel better about yourself. Several studies have shown that when people increase their activity they also increase their self-confidence, self-acceptance, and sense of personal worth and feel more comfortable in their bodies. As chapter 8 will make clear, these are exactly the tools you need to be successful at implementing all the other health-promoting strategies detailed in this book. Chapter 10 gives you a game plan to get you up and moving.
Beyond Food and Activity
So I’ve shot down dieting and exercise as sure-fire weight-loss techniques. Few people think beyond these two pieces of the puzzle, but there’s a much bigger picture that’s less self-evident, much of which is poorly understood. For example, a pregnant mom’s nutrition and other habits affect the offspring’s body weight later in life. It’s also well established that stress, sleep deprivation, even viral infections, microbes in your gut, and environmental toxins also play a role. Let’s take a look at some of these additional contributors to weight. We’ll keep our focus on lifestyle and environmental factors, rather than pre-birth or genetic factors.
Stress
Uh-oh. Job interview coming up. The mere thought of it stimulates your nervous system to get charged. When the body is challenged by almost anything, from getting out of bed in the morning to running up a flight of stairs or having to stand up and give a talk, the brain activates the sympathetic nervous system, the so-called “flight or fight” response, which causes the release of the stress hormones, among them cortisol and epinephrine. Their net effect is to make a lot of stored energy (glucose and fat) available to cells. Cells are then primed to help the body get away from danger.
If you were a caveperson innocently picking berries when suddenly you come nose to nose with a saber-toothed tiger, you’d appreciate this. The flood of energy might help you scamper up that tree.
Couch Potatoes Created in the Womb?
You are not only what you eat, you may also be what your mother ate. Several studies find that if your mother dieted during her pregnancy, you’re more likely to be heavier as an adult. One study found that the adult children of dieting pregnant women were less likely to be physically active than the adult children of women who didn’t diet. This suggests that conserving energy to protect against the food insecurity you experienced in utero may now be “hardwired” into your genetic memory.
68
However, with mental stress, the body pumps out these hormones to no avail. Fighting or fleeing won’t help when the “enemy” is your own mind. Nonetheless, your bloodstream is flooded with nutrients, and sugar storage mechanisms are suppressed. With nowhere to go, the unused sugar in your bloodstream gets converted to fat.
Cortisol acts both to pack the fat away into storage and as a powerful appetite stimulant, prompting you to eat more and get even more nutrients into your bloodstream. Stress also results in suppression of the release of growth hormone, which would have reduced fat storage and sped up your metabolism. It’s not surprising that we see links between chronic stress and higher weight.
69
70
Also, more stress results in less nutritious eating, which contributes to the higher weight.
69
It may be that stress doesn’t act alone. In one very interesting experiment, scientists subjected mice to stress by locking them in a cage with a more aggressive mouse. Some of the mice were given standard feed, and the others were fed the mouse equivalent of a processed food diet. The stressed mice eating the processed foods gained a significant amount of weight, much more than the stressed mice fed the standard feed. They also gained significantly more weight than mice consuming the same processed food diet that were not subject to stress. If this translates to humans, it suggests that it’s not just the stress, but the combination of stress and a nutrient-poor diet, that does you in.
71
In another interesting experiment, researchers injected a virus that replicates in neurons with receptors for leptin. The virus was engineered to carry a gene for a green fluorescent protein. The presence of the protein enabled researchers to trace the path of the virus as it moved through the brain. It turns out that in addition to sensing leptin levels, the neurons with leptin receptors also received input from a region of the brain that plays a role in emotion.
72
In other words, the brain section that modulates emotion was, just like leptin, influencing appetite and energy expenditure.
Sleep
Can you dream your way to maintaining a lighter weight? As wild as the idea sounds, the relationship between sleep deprivation and weight gain is actually well established.
73
74
75
76
77
Several studies also detail the link between sleep loss and the metabolic hormones.
78
79
Have you ever had a restless night followed by a day when no matter what you ate you never felt full or satisfied? If so, you probably experienced the workings of leptin and ghrelin. Insufficient sleep drives leptin levels down, which means you don’t feel as satisfied after you eat. Lack of sleep also causes ghrelin levels to rise, stimulating your appetite so you want more food.
That’s what happened to the twelve men in this research study.
79
When sleep was restricted, leptin levels went down and ghrelin levels went up. The men’s appetites also increased proportionally, as would be expected. Also interesting was that their desire for high-carbohydrate, calorie-dense foods increased by a whopping 45 percent!
Strange but True: Viruses, Bugs, and Toxins
Is weight gain contagious? Can you blame it on the bugs in your gut? How about the pesticides in your food? Turns out there’s scientific evidence supporting all these factors playing a role in some people’s weight gain. There are many different—and surprising—factors that influence our eating habits and fat deposition. Here’s the scoop.
A Weight-Gain Virus
Scientists were surprised to find that heavier people were four to six times more likely to have a cold-like virus, called adenovirus-36, than leaner people. Inoculating mice, rats, chickens, and monkeys with the virus results in the animals gaining weight and body fat—without eating more.
80
81
Researchers didn’t try to infect humans, but they did expose human stem cells—the blank slate of the cell world—to the virus and found that they turned into fat cells.
82
They didn’t just change, they stored fat, too.
Certainly we have a history of blaming several diseases and conditions on diet, only to find out later that a microbe was to blame. Consider ulcers. Long thought to be a product of high stress and a poor diet, most ulcers are now known to be caused by the bacterium H. pylori. Or consider heart disease: To date, three different microbes have been discovered that are thought to contribute to clogged arteries. There is also a well-established association between periodontal disease and heart disease that is attributed to certain bacteria.
83
Strong evidence associates several viruses with weight gain.
84
Bugs Making Us Fat
You might not be out of line to link a burgeoning belly to the bugs in your tummy. The three to four pounds of bacteria swilling around in our bellies not only play a central role in our digestion, but are also important energy regulators.
85
And it turns out that some microbes are better at wringing calories out of your meals than others. Transferring these high-octane bugs from fat mice into lean mice causes the lean mice to plump up.
86
Fatter people tend to have a significantly greater proportion of one of the two main types of bacteria found in the gut, known as Firmicutes, than the other, known as Bacteroidetes. Detailed molecular analyses show that the Firmicutes are much better at extracting calories from food.
87
When researchers spent a year meticulously measuring the gut flora of the heavier volunteers as they tried to lose weight by eating low-calorie diets, they actually discovered that the proportion of Firmicutes in their digestive tracts rose and the proportion of Bacteroidetes fell.
87
This discovery could easily explain why it becomes harder and harder to lose weight through dieting.
Think about this. The same bowl of pasta yields a different number of calories for each eater. Rodents raised in a sterile environment and lacking in gut flora need to eat 30 percent more calories just to remain the same weight as their normal counterparts.
88
What causes an individual to have their particular mix of gut flora isn’t clear. But perhaps some change, such as a food additive or antibiotic use, has caused a fundamental shift in these bugs, making it easier for many people to gain weight.
The Fattening Effect of Pollution
The jury is out on the relationship between pollution and weight, but the connection is certainly plausible, and it’s a hot topic in research.
89
It is well established that dioxins, pesticides, and other compounds disrupt hormonal function. Since your hormones play a large role in weight regulation, it’s not a big leap to assume that toxins also disrupt your ability to effectively regulate your weight.
Compounds that change hormonal function are called “endocrine disrupters,” and those that are known to increase fat production are more specifically labeled “obesogens.”
90
91
92
Tributyltin chloride, or TBT, is an example of an obesogen that has been well studied in animals.
91
93
Frogs and mice injected with miniscule doses of TBT got very fat. And prenatally exposed mice are 10-15 percent heavier than control mice.
TBT is ubiquitous in our environment. Originally part of marine paints, it is now used in fungicides, wood preservatives, and in the manufacture of PVC plastics (used in water pipes and food packaging). A limited study pegs the average human TBT blood concentration at 27nM, or just slightly higher than what has shown to affect laboratory animals.
94
Although a causative effect has yet to be established, production of industrial chemicals in the United States, including TBT, closely parallels the weight increase observed in the United States.