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Eating the Way Our Bodies were Designed

The Who, What and Why of Intermittent Fasting

Talk of intermittent fasting is making the rounds as a way to lose weight and stave off or alleviate chronic disease, but is it right for everyone or just a fad?

We’ve asked Calvert Internal Medicine Group Endocrinologist Dr. Julie O’Keefe to help readers understand what intermittent fasting is, who can benefit from it and why it can be effective.

“Losing weight in theory is very simple, but in practice is very difficult,” said Dr. O’Keefe. “Time-restricted eating is a strategy that designates periods of eating and periods of fasting. The periods of eating and fasting can vary but they have in common a period of time when there is no food consumption—usually eight or more hours.”

Availability of Food

The ability of humans to go without food for long periods of time is built into our body systems. Primitive people had to hunt, they had to gather, and they had to prepare and store food. Food was not available to consume 24/7.

Our bodies can go without food for several hours, for several days, and even longer because our bodies are developed to store fat. In other words, human bodies are equipped to encounter periods of fasting.

Humans evolved to be in sync with the day/night cycle, or a circadian rhythm. Our metabolism has adapted to daytime food and nighttime sleep. But what if due to technological advances, humans have the option to be alert and active during the night and have access to food at all hours?

How Human Bodies Process Food

Our bodies need nutrients from food and drink in order to work properly and keep us healthy. Proteins, fats, carbohydrates, vitamins, minerals and water are nutrients. The digestive system breaks these nutrients down into parts small enough for our bodies to absorb and use for energy, growth and cell repair.

The digestive process starts with the first bite of food but can take up to eight hours for food to pass through the stomach to the small intestine.

“Intermittent fasting designates a period of time, usually greater than eight hours, during which we do not take in calories,” said Dr. O’Keefe. “This fasting state allows our body time to process the nutrients we have eaten and to burn fat.”

Timing of Meals

There are two schedules of intermittent fasting that most people follow. The most common is the daily 16-hour-no-food/8- hour-food schedule. This means that if you normally eat your first meal at 8 a.m., you have your last meal eight hours later, at 4 p.m. You can change the time of consuming food according to a schedule that works best for you. So, if your family eats dinner at 6 p.m., then you adjust and don’t eat breakfast until 10 a.m. The idea is that you eat only during an 8-hour time period—and that’s it. No more food or snacking outside of that time period. You can drink water, but ideally you are not putting any calories in your body during that 16-hour time period of fasting.

Another intermittent fasting schedule is more restrictive. The 5-2 schedule follows that for five days out of the week you eat when you want and then two days out of the week you are just eating one meal a day, consisting from 500-600 calories and drinking water or black coffee for the remainder of the day.

Benefits of Intermittent Fasting

According to the National Institutes of Health (NIH), the majority of available research shows that intermittent fasting is effective at reducing body weight, decreasing fasting glucose, decreasing fasting insulin and reducing insulin resistance, which is the precursor of Type 2 Diabetes.

Just changing the timing of meals, by eating earlier in the day and extending the overnight fast, significantly benefited metabolism even in people who didn’t lose weight.

Is Intermittent Fasting Right for Me?

As with starting any new diet or health regimen, people should consult their primary care doctor to ensure that intermittent fasting is safe for them.

“Adherence is a major factor in the success of any dietary intervention,” Dr. O’Keefe said. “Patients need to choose a dietary regimen that will work in their lifestyle. If someone is interested in intermittent fasting, I explain the process and let them decide what would work best for them.”

Foods Included in Intermittent Fasting Program

“There are no specific food restrictions with intermittent fasting. However, all prescribed diet programs should emphasize the intake of as many unprocessed foods as possible: fresh vegetables, lean meats and fruits. Though you may be following a restricted time period to eat, if you spend the time eating take-out and junk food, you will not have successful weight loss.” said Dr. O’Keefe.
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