Intermittent Fasting

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What is Intermittent Fasting?

Fasting of all kinds have been done for many years, most due to influence from many world religions. Now a type of fasting called Intermittent fasting is currently one of the more popular ways people are attempting to lose weight and simplify their lifestyle. Contrary to a ‘diet’, which is changing the foods you eat, intermittent fasting (IF) focuses on changing the times you eat. There are several different ways this can be done:

  • 16/8
    • Fast for 16 hours then eat for 8 hours, most popular.
  • 5:2
    • On two non-consecutive days eat 500-600 calories, eat normally other days.
  • Eat-Stop-Eat
    • 24 hour fasts 1-2x/week
  • Alternate-Day Fasting
    • Day of normal eating followed by either 500 calorie day or complete fast and repeat.

How Does It Work?

Most of us have unknowingly done IF at some time in our lives when we eat a normal dinner on Friday night then slept in on Saturday and don’t eat until lunch/brunch time. To understand how IF works we must first understand the difference between the fed and fasted states of our body.

Your body is in the fed state when it is digesting and absorbing food. This state begins when you start eating and lasts 3-5 hours depending on the meal you ate. In this state it is proposed that it is very hard to lose fat because this is also when insulin levels are high.

After these 3-5 hours your body enters the post-absorptive state, which is when you are no longer absorbing foods. This state will last about 8-12 hours. After this you will finally enter the fasted state, which is when it is easiest to burn fat because our insulin levels are lowest. However, our bodies are rarely in a fasted state when we eat a traditional 3 meals a day. The fasted state is where our bodies will supposedly start using fat as a primary source of energy.

Does This Actually Work?

For those who follow the popular 16/8 plan, it is not unusual for some people to lose weight just because they tend to eat less within the restricted hours. The best answer to this question is that it depends on the individual’s lifestyle. This pattern of eating may appeal to those who like a structured way of eating.

A recent study from JAMA showed that there was not significant difference in the IF group and a simple calorie restriction group. This study was done over the course of a year but the IF group had a 25% dropout rate leading us to think this pattern of eating may not be effective long-term. It is important to note that eating fewer meals will require you to eat more fruits and vegetables at each meal in order to meet your daily adequate intake.

Who Shouldn’t Try Intermittent Fasting?

IF is definitely not for everyone, especially for those who are underweight, have an eating disorder, or conditions that may require medication such as diabetes to help with blood sugar control. Some medications may need to be taken with a meal or within a certain timeframe before or after a meal.

Some studies have also shown that IF affects men and women differently and is not as effective, and possibly dangerous for women. Hormone imbalance, menstrual disturbances, and disordered eating. Hunger and weakness are the main side effects but tend to diminish over time. As you consider attempting any kind of IF remember to always consult your physician before attempting significant lifestyle changes.

Websites to check out:

Intermittent Fasting 101 – The Ultimate Beginner’s Guide

Today’s Dietitian

Does fasting on alternate days work? A new study weighs in

Created by: Raul Palacios BS, TTU Dietetic Intern
Hospitality Dietitian Mindy Diller, MS, RDN, LD   mindy.diller@ttu.edu 

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