Empty calories, like low-grade gas, can bring your engine a sputtering stop.
But nutrient-rich foods can help you run lean and clean.
Wilbur compares our fuel requirements to those of the vehicles we drive. “It’s no more than basic gas in a car,” she says. This analogy is refreshingly straightforward. How the body processes biological fuel, however, is anything but simple.
Metabolism sets the stage for our fuel usage. Each person has their own basal metabolic rate (BMR). BMR is the energy your body expends at rest to maintain normal bodily functions—the amount of energy you would burn if you weren’t active all day.
with a GI of 15, all but two are vegetables. Whole grains also tend to score lower than their refined counterparts, such as white bread’s 71 compared with rye’s 34 or multi-grain’s 48.
of them at one time, either.
A number of resources are available if you want to learn more about GI and GL. The University of Sydney, which has done a lot of GI research, maintains a GI database at www.glycemicindex.com.
Energy production is such a vital function that the body likes to store fuel, also known as calories, in several different forms. The most common (and bemoaned) form is fat, known technically as adipose tissue. This serves as long-term storage to protect the body against potential calorie shortages in the future.
Related to glycogen is glucose. Commonly refer­red to as blood sugar, glucose needs to be maintained at steady levels throughout the day or fatigue and dizziness can set in. To prevent that from happening, the liver breaks down glycogen and releases it into the bloodstream as glucose as directed by the pancreas, the organ responsible for monitoring blood-sugar levels.
But there’s a catch. “The glycogen that we store in our muscle is exclusively for the muscle’s use,” Sasson says. “If I’m starving and I haven’t eaten for hours and hours, and I have glycogen stored in muscle, it won’t give it up. It’s only for that particular muscle.” What would seem like a disadvantage is actually a survival mechanism; this feature allowed early humans to either fight danger or flee from it even if they hadn’t consumed anything substantial in days. “If our bodies had relinquished that kind of stored energy, then we wouldn’t have survived as a species,” Sasson explains.
The liver is another matter. Sasson says this organ “is very generous” with its glycogen supply, but “you can’t store that much liver glycogen.” Despite its limitations, this form of glycogen is what the body often uses when you first get up in the morning. Having gone without food for hours, the body draws upon liver glycogen, but its finite nature tends to offer only enough energy to get the body minimally moving—not enough for you to feel fully energized.
That concept can get lost in the morning rush to get going, which means that all-important morning meal is often overlooked. Wilbur compares skipping breakfast to “kind of like starting the car and driving cross-country without filling up the tank.” Mashek notes that not eating in the morning, a common strategy among many would-be dieters, is eventually self-defeating. “It will likely cause you to be more hungry at the next meal, which may change your metabolism, and lead to over-consuming calories, only to store those extra calories as fat,” he explains.
Just as the storage of glycogen in muscles enabled our ancestors to make quick getaways when needed, the storage of fat in adipose tissue let them cart around extra energy as a defense against calorie shortages. “In times of famine, people were able to store this fat as a fuel source, and that’s how they survived,” notes Sasson. As a result, in sharp contrast to today’s societal standards, carrying some degree of excess fat on your body was once considered a virtue—it was a sign that you had the means to afford extra calories.
What happens to a particular meal as it goes through the metabolic process largely depends on the amount of energy already stored in the body, particularly in the adipose tissue. When a person eats something highly processed and relatively low in nutrition—for example, a large plain bagel topped with a slab of cream cheese—most of that bagel is going directly into fat tissue, especially if they had a big meal not long beforehand.
Sasson certainly agrees. “Whole wheat bread with peanut butter is much better than a bagel with cream cheese,” she says, explaining that the bagel is “not really protein, and it’s a simple carb. You’ve had a lot more calories consumed, but in an hour you’re hungry.” On the other hand, she says that the pairing of a complex carbohydrate such as whole wheat and a protein such as peanut butter helps sustain your energy.
That is why Sasson encourages making whole foods—the biological equivalent of high-grade gasoline—the centerpiece of your family’s meals. “The more complicated a food is, the more whole it is from nature, the longer it takes to digest,” she says. “Your body becomes a digesting machine. When we eat very highly processed food, in a way, industry has already digested it for us.” Foods that promote a sustained release of energy along with a fuller, more satisfied feeling include nuts, legumes (such as dried beans, lentils and peas), eggs and oatmeal, along with fresh fruit and vegetables.