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Intermittent Fasting 101: A Simple Guide for Lasting Results

Welcome to intermittent fasting 101!

In a world inundated with diets and eating plans, intermittent fasting has emerged as a popular tool in health promotion.

If you’ve heard about intermittent fasting but aren’t sure where to begin, this simple guide is for you!

Salad Plate next to a blue alarm clock; intermittent fasting 101
Intermittent fasting 101

What is Intermittent Fasting?

Intermittent fasting (IF) is not a diet in the traditional sense. It’s an eating pattern that alternates between periods of fasting and eating.

Unlike conventional diets that focus on specific foods or calorie counting, IF is all about when you eat.

How Does It Work?

IF involves cycling between two main phases, a fasting window and an eating window.

During the fasting window, you do not eat any calories. Non-caloric beverages are permitted during this window including water, tea, and black coffee.

The eating window is where you get in your total calories for the day. These periods vary based on the specific IF method you choose.

Brown plate with a variety of foods at the top; the lower half of the plate has the word "fast" spelled out.
IF involves a fasting and eating window.

What Happens to Your Body When Fasting?

Fasting for an extended period of time triggers changes in the body as it adapts to not having food.

These changes allow the body to conserve energy and use stored resources more efficiently.

Read on for the science behind intermittent fasting.

Insulin Decreases

Insulin is the hormone that is responsible for moving glucose into your cells for energy or storage.

When you stop eating, your insulin levels drop. Lower insulin levels encourage the body to use stored fat for energy.

Insulin defined in a dictionary magnified by a magnifying glass; intermittent fasting 101
Fasting causes insulin levels to drop.

Fat Breakdown Increases

As insulin levels decrease, your body becomes more receptive to hormones like norepinephrine, which signals the fat cells to break down stored fat.

This stored fat is used for energy.

Calipers measuring body fat on upper arm.
Fasting helps promote fat breakdown.


The body can enter a state of ketosis following prolonged periods of fasting.

Ketosis allows the liver to convert fatty acids into ketones, which provides the body with an alternative energy source.

Fuel knob with 2 options-ketones or glucose
Ketones are an alternative fuel option for the body.

Cellular Repair

Cells may undergo repair processes that help maintain overall cellular health.

This may contribute to the anti-aging effects of intermittent fasting.

Types of Intermittent Fasting

There are several different types of IF each with its unique approach.

Various fasting schedules accommodate lifestyles, preferences, and goals.

Not everyone’s schedule or dietary needs are the same, so different eating windows allow for flexibility and customization.

16/8 Method

The 16/8 strategy involves fasting for 16 hours and restricting your eating to an 8-hour window.

For example, you may eat between 12 pm and 8 pm. Then fast from 8 pm that evening to noon the next day.

16/8 intermittent fasting visual clock plate
16/8 IF restricts eating to an 8-hour window.

5:2 Method

There are various ways to follow this method.

The 5:2 diet entails following a regular, nutritious diet for five days each week while restricting food intake on the remaining two days.

Eat-Stop-Eat Method

This method involves fasting for a full 24 hours 1-2 times per week.

For example, you may avoid eating dinner from one day to dinner the next day.

Alternate-Day Fasting Method

In this IF strategy, you alternate between fasting days and regular eating days.

Fasting days may not be a true fast, but involve minimal calories.

Notepad with intermittent fasting written on the top paper next to a small clock and plate.
There are various IF methods.

Benefits of Intermittent Fasting

Why is fasting good? This eating method offers several benefits. Read on to learn more!

1. Weight Loss

By restricting your eating window, you may be able to create a calorie deficit, the key to weight loss.

For some individuals, the structure of intermittent fasting is all they need to reduce their food intake.

In addition, IF can be easier to maintain than other weight loss diets because it does not involve complex meal planning or counting calories.

Initial findings on intermittent fasting in the treatment of obesity are promising, however, more research is needed.

Much like other eating strategies, IF is not a magic bullet, however, it can be a helpful tool when combined with nutritious foods and regular exercise.

Woman celebrating her weight loss using intermittent fasting 101
IF is a promising method in obesity treatment.

2. Improved Sensitivity to Insulin

IF has shown promise in both treating and preventing type 2 diabetes.

Diabetes is a dietary disease that is caused by too much sugar in the blood.

Giving the body a break from eating appears to help regulate blood sugar and improve insulin sensitivity.

3. Anti-Aging / Enhanced Autophagy

Autophagy is like a cleanup crew that gets rid of old or damaged parts of the cell. It makes room for new and healthy parts to grow.

This keeps our cells and body working properly which promotes healthy aging.

Fasting has been shown to trigger autophagy which extended the lifespan in rats in research studies.

You can learn more about autophagy in this Age-Defying Dietitian blog post – “Top 5 Foods that Promote Autophagy“.

The word "autophagy" spelled out in colorful stamps
Autophagy promotes healthy aging!

4. Reduced Inflammation

Some research suggests that IF may reduce markers of inflammation in the body.

Chronic inflammation is associated with various diseases like diabetes, heart disease, and dementia.

How to Get Started with Intermittent Fasting 101

  • Choose the Right Method: Select an IF method that suits your lifestyle and preferences.
  • Start Slowly: If you’re new to fasting, begin with shorter fasting periods and gradually increase the duration.
  • Stay Hydrated: Drink plenty of fluids during fasting periods to stay hydrated.
  • Eat Nutrient-Dense Foods: Focus on whole, unprocessed foods during your eating windows to ensure you meet your nutritional needs.
  • Listen to Your Body: Pay attention to your body’s hunger cues and adjust your fasting schedule accordingly.
Man drinking water out of an orange water bottle; hydrating while engaging in intermittent fasting
Drink plenty of water while engaging in IF.

Are you interested in how collagen supplements impact – “Does Collagen Break a Fast?“.

Safety Considerations

Intermittent fasting is not for everyone. Consult your healthcare provider before beginning a fasting regimen.

The risks associated with IF include dehydration, hypoglycemia/low blood sugar, malnutrition, and disordered eating.

Safety is paramount when it comes to any dietary fasting method.

Road sign that says "safety first" signifying safety as part of intermittent fasting 101
Safety is important with any fasting method.

Takeaways: Intermittent Fasting 101

IF is a flexible and effective eating strategy that may promote weight loss and improved health.

Its benefits include weight loss, improved insulin sensitivity, increased autophagy, and a reduction in chronic inflammation.

Intermittent fasting is not for everyone and does pose some possible risks and side effects.

Talk to your healthcare provider before starting any fasting strategy.

With the right guidance, intermittent fasting can support a healthier lifestyle and longevity!

A blue alarm clock surrounded by plates of healthy foods
Intermittent fasting is a helpful tool in the pursuit of wellness!

Hungry for More?

Interested in more information on nutrition for healthy aging?

Check out the Age-Defying Dietitian’s blog for more healthy aging content!

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