Most scientists now believe that obesity is more complex than simply eating too much and moving too little. In fact, some propose that there is an environmental component to obesity. In other words, factors in the environment make it harder for humans to control their body weight.
Have we oversimplified the obesity problem? If you subscribe to the calories in, calories out model, a person will gain a pound when they consume an additional 3,500 calories beyond what their body needs for maintenance. If you don’t burn those calories off through exercise, you will theoretically gain a pound. Of course, that extra pound of weight could be mostly body fat or a portion of it could be muscle tissue. The latter would be more likely if a person strength trains.
But, maintaining energy balance is more complex than it might seem. You have a host of hormones as well as environmental influences that impact how rapidly your body uses energy. Even the macronutrient composition of a person’s diet is a factor. For example, refined carbohydrates cause a greater release of insulin and this makes it easier to store fat. Plus, dietary composition impacts appetite as well. What sounds simple on the surface is actually quite complex!
How might environmental factors influence weight loss? Factors in the environment can turn genes involved in fat storage and fat breakdown on or off through epigenetic mechanisms. Epigenetics is the modification of gene expression that doesn’t involve changes to the actual genetic code. Rather, genes, the information you inherited from your mom and dad, is turned on and off by factors like diet, exercise, exposure to toxins, and more. So, even if an individual has a strong genetic tendency towards obesity, through lifestyle they can potentially reduce the expression of these genes and not become obese. That’s why lifestyle is so important!
So, what are the environmental factors that may impact a person’s risk of obesity?
Environmental Chemicals
Much of the focus on environmental causes of obesity centers around obesogens, chemicals in the environment that alter the activity of hormones that control body weight. We’re exposed to many of these chemicals every day without being aware of it. One of the best studied is bisphenol-A (BPA), a component in some types of plastic. Exposure to BPA, particularly early in life, may alter the size of an individual’s fat cells, making them larger. Keep in mind, this is based on animal research and is more difficult to study in humans. There’s also evidence in animals that BPA disrupts hormones involved in fat metabolism and alters how glucose is handled by the body.
Due to concerns about obesity, the FDA has banned the use of BPA in certain children’s products, like sippy bottles, to reduce exposure. Unfortunately, BPA alternatives are springing up and research suggests that they may be just as harmful as BPA. Plus, BPA and chemicals in plastic are only the tip of the iceberg. Most commercial scented products contain chemicals called phthalates that may have similar effects on the body.
Some research even suggests that BPA and phthalates may alter the body’s “set point.” When you try to lose weight, your body fights to bring your weight back to an established set point that it deems safe. Your body seems to have an internal “thermostat” that helps regulate how much body fat you have. If you go too far below your set point, you feel hungry and move less to help bring you back to your set point weight and, if you have a higher set point, you’ll struggle more to get your weight down.
Temperature-Controlled Environments
These days, we spend most of our time in temperature-controlled rooms, but at one point in history, humans were exposed to temperature extremes – the heat of summer and blistering, cold winters. Due to a relatively warm, static environmental temperature, our bodies no longer have to work as hard to maintain an appropriate body temperature. When you are exposed to the cold, your body has a mechanism for raising your body temperature to protect against the cold and it’s called shivering. Shivering involves muscular contractions that require energy. So, you burn additional calories when you shiver. This doesn’t happen when you live in an environment where the temperature rarely changes. We may be a little TOO comfortable for the health of our waistlines!
Exposure to Light at Night
At one time, people were more likely to turn in when the sun went down for a restful night’s sleep. These days, people spend hours after dark on an electronic device where they expose their eyes to blue light, the light of a wavelength known to disrupt sleep. Plus, blue light alters the release of hormones involved in sleep, like melatonin. These changes disrupt the body’s natural biological rhythms, known as circadian rhythms.
Circadian rhythms are closely tied to factors such as appetite, food choices, and metabolism. Plus, the timing of when we eat has changed. More people eat dinner later and snack into the evening. Some research suggests that the timing of what we eat impacts how likely we are to gain weight due to circadian factors. In the evening, our body is set up for sleep, not to process food. In fact, a study carried out by researchers at Northwestern University found that participants who got up later in the day and ate dinner later consumed an additional 248 calories daily, on average. They also were less likely to make healthy dietary selections.
Other Potential Obesity Factors
These aren’t the only factors that potentially make it harder to lose weight, irrespective of calorie intake. Other proposed factors mentioned in a 2009 overview include increased portion sizes, an increase in restaurant dining, the lack of easily accessible sidewalks, easy availability of snack foods, low-grade inflammation, a possible viral etiology, in utero factors, changes in sleep patterns, and the use of certain medications. So, obesity is more complex than we thought!
References:
Maturitas. 2011 May; 69(1): 41–49.
Science Daily.com. “Epigenetic switch for obesity”
ObesityAction.org. “Body Weight “Set Point” – What We Know and What We Don’t Know”
PsychologyToday.com. “Body Weight in the Time of Climate Control”
New York Times Well. “Central Heating May Be Making Us Fat”
ISRN Obes. 2012; 2012: 437198.
Curr Opin Endocrinol Diabetes Obes. 2016 Oct;23(5):353-9. doi: 10.1097/MED.0000000000000276.
SleepFoundation.org. “People Who Eat and Sleep Late May Gain Weight”
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