How do we know when to eat?

An illustration of the Arc protein. Original image from Wikimedia Commons.
An illustration of the Arc protein. Original image from Wikimedia Commons.

When Sharon was 14, she quit eating lunch at school. She had been gradually gaining weight and her mother would occasionally send a troubled look her way when they were shopping for clothes. Sharon was ashamed but couldn’t help it; she lived in a town where driving was the norm and there were only so many exercises she could do in her dark bedroom at night without waking her baby brother. So instead, she watched with increasing embarrassment as her pants grew tighter and her sleeves were topped with small rolls of flesh.

So she started donating her school lunches to the boys she hung around with, who happily obliged. She felt her stomach tightening in ropes as she enviously watched them bolt down the soft bread and run off to play dodgeball, their bony limbs clearly outlined beneath khaki uniforms. Even the other girls were eating lunches of crustless sandwiches and Pop Tarts and staying slim. It wasn’t fair, she thought, as she stared at her rounded thighs.

Every night, Sharon forced herself to only take one spoonful of dinner. Waiting for her mother to finish cooking was torture as her stomach rolled and grumbled, squalling that 6 o’clock was a mealtime. It never changed. To this day, eight years later, she still eats dinner at 6 o’clock or hears about it from her stomach.

Most of us experience the phenomenon of “dinnertime”— a time of day when we know we’re hungry. It’s different for everyone and may vary across a lifetime, but it doesn’t entirely adhere to nature. The way our brains time meals is still unclear to scientists.

A study published Nov. 5 in the journal Hippocampus puts forward the theory that sweet sensations help us mark the ends of meals. (Thus, dessert.) The researchers, a combination of scientists from Georgia Regents University,Charlie Norwood VA Medical Center and Georgia State, hypothesized that eating sweets sets off the dorsal hippocampus neurons, which create episodic memory. Episodic memory is what sets a particular time apart from the regular flow of existence, the way meals begin and end.

The researchers fed sugar solutions to rats and watched the activity in a synaptic plasticity marker in the hippocampus commonly known as Arc. Synaptic plasticity plays a role in creating memories. The rats with less experience with sugar showed significantly higher Arc activity, possibly correlated with creating new memories. They also tested whether saccharin (sugar substitute) could be sufficient to create the Arc activity needed, and it seemed to be true. That could provide an in for those who want to reduce their meal intake and have a noncaloric sweetener afterward to solidify the memory. (However, saccharin in some cases has been linked to cancer in laboratory animals, so buyer beware.)

Taking a look at the way we behave with food is critical to learning how to control obesity and food-related illnesses. Type 2 diabetes, which is linked with obesity, is a rampant problem in the U.S. The Centers for Disease Control and Prevention recently released its 2014 Diabetes Report Card, showing that the number of adults diagnosed with diabetes (both types) has quadrupled in the past three decades. Type 2 accounts for 90-95 percent of the total cases in the U.S.

The risk is greatest for American Indians and Alaska Natives, who lead among the ethnicities primarily represented in the U.S. by more than 2 percent. Poor eating habits are often the result of poverty, which is also common among American Indians and Alaska Natives.

Of course, weight gain is not always equally spread, even if two people eat the same things every day. I’ve written about that issue before, but genetics also play a strong role in how people gain weight. The way we process different foods can depend on where our genetics come from and how they express themselves. To know why we eat what we eat and when will affect how our bodies control themselves.

For Sharon, who is now 22 and still doesn’t eat lunch, it may be more of a struggle of identity. It’s hard to not eat lunch when you have to go out to business luncheons with clients, but it’s also hard to be the only chubby one in the office. The way she eats should be personalized to her, and she’s struggling to find a way to avoid the awkwardness without regretting it later.


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