Intermittent Fasting: Results and Experiences

Intermittent fasting has gained massive popularity. But does it actually work better than regular dieting? Here's what the research says.

Intermittent fasting — what is it all about?

Intermittent fasting (IF) is an eating pattern where periods of eating and fasting alternate. It is not a diet in the traditional sense — IF does not tell you what to eat, but when to eat.

Intermittent fasting has become one of the most popular weight management methods of the 2020s. But does it hold up under scientific scrutiny? And is it suitable for women in particular?

In this article, we examine the research results on intermittent fasting, practical experiences, and who it is suitable for — and who it is not.

The most common IF methods

There are several versions of intermittent fasting:

16:8 method: You eat within an 8-hour window and fast for 16 hours. For example, eating from 11 AM to 7 PM and fasting from 7 PM to 11 AM. This is the most popular and easiest to implement.

5:2 method: You eat normally 5 days a week and restrict calorie intake to 500–600 kcal on 2 days per week. Fasting days are not consecutive.

Eat-Stop-Eat: A 24-hour fast 1–2 times per week. For example, from dinner to the next day's dinner.

OMAD (One Meal A Day): You eat only one meal per day. This is the most extreme form and rarely recommended.

Most research and practical experiences are based on the 16:8 and 5:2 methods.

What does research say about results?

Weight loss

A meta-analysis of 27 studies showed that intermittent fasting produces significant weight loss: an average of 0.8–13% of starting weight during the study period (Welton et al., 2020). The weight loss was comparable to a traditional calorie-restricted diet.

Important note: IF is not a magic solution. It works because it helps many people naturally eat fewer calories. When the eating window is limited, late-night snacking is eliminated and the total number of meals decreases.

Metabolic effects

Studies have shown several positive metabolic effects:
- Improved insulin sensitivity (Halberg et al., 2005)
- Decreased inflammatory markers
- Activation of autophagy (cellular cleaning process)
- Improved cholesterol values

These effects are especially significant for those at risk of metabolic syndrome and type 2 diabetes.

Muscle mass and performance

Concern about muscle loss is common. However, studies have shown that IF combined with strength training and adequate protein intake preserves muscle mass just as well as a traditional meal pattern (Tinsley & La Bounty, 2015).

The key is to ensure you get enough protein during your eating window — at least 1.6 grams per kilogram of body weight per day.

Practical experiences: what users report

Intermittent fasting divides opinions. The most common positive experiences include:

- Simplicity: "No need to think about breakfast — one fewer decision per day"
- Energy: "I feel clearer in the morning without breakfast than with it"
- Sense of control: "It is easier to manage eating when there is a clear time window"
- Digestive comfort: "Stomach issues decreased when the digestive system gets to rest"

The most common negative experiences include:

- Initial hunger: "The first 1–2 weeks were challenging"
- Social situations: "Difficult when friends go for brunch"
- Irritability: "I was grumpy in the mornings before my body adjusted"
- Overeating during the eating window: "I noticed I was eating too much at once"

IF and women — special considerations

This is a critical topic that is often overlooked in IF discussions. Research suggests that women's bodies respond to fasting differently than men's.

One study found that intermittent fasting improved insulin sensitivity in men but worsened it in women (Heilbronn et al., 2005). In another study, women's cortisol levels rose more on fasting days than men's.

Women's hormonal systems are more sensitive to changes in energy availability. Overly aggressive fasting can:
- Disrupt menstrual cycles
- Raise cortisol levels
- Affect thyroid function
- Impair fertility
- Increase anxiety and insomnia

This does not mean IF is unsuitable for women — but it does mean women should start more cautiously.

Safe starting approach for women

If you want to try intermittent fasting, we recommend the following gradual approach:

Week 1–2: 12:12
Start with a 12-hour fast, for example from 8 PM to 8 AM. This is close to a normal eating rhythm and helps your body adjust.

Week 3–4: 14:10
Extend the fast to 14 hours, for example from 7 PM to 9 AM. Research suggests this is already sufficient for many benefits.

Week 5 onward: 16:8 (optional)
If 14:10 feels easy and you are feeling well, you can try the 16:8 method. Listen to your body — if your menstrual cycle is disrupted, return to a shorter fast.

Important rules for safe IF:
- Even on fasting days, drink enough water, tea, and coffee
- Do not restrict calories too much during the eating window — eat enough
- Ensure adequate protein intake
- Do not combine IF with a strict diet simultaneously
- Listen to your body — if you feel unwell, stop
- On training days, you can eat more

Who should not try IF?

Intermittent fasting is not suitable for:
- Pregnant or breastfeeding women
- Underweight or malnourished individuals
- Those who have or have had an eating disorder
- Type 1 diabetics without medical supervision
- Those under 18 years old
- Those taking blood sugar-lowering medications

IF vs. traditional calorie restriction — which is better?

Based on research evidence, intermittent fasting and traditional calorie restriction produce very similar results in weight loss and health markers (Cioffi et al., 2018). IF is not superior — it is an alternative tool.

IF's biggest advantage for many people is its simplicity: instead of counting calories at every meal, you have one clear rule — eat within this time window.

On the other hand, calorie counting suits some people better because it does not restrict when they eat. The best method is the one you can follow consistently over the long term.

How to combine IF and exercise?

Many wonder whether they can exercise in a fasted state. Studies show that light and moderate exercise works well in a fasted state. Fat metabolism is actually more efficient in a fasted state.

However, heavy strength training or intense interval training should be timed for the early part of the eating window so recovery nutrition can be consumed after the workout.

Practical recommendations:
- Light exercise (walking, yoga): Fine during fasting hours
- Moderate exercise (easy jogging): Fine during fasting hours
- Intense training (HIIT, strength): Schedule during the eating window

Summary: who is IF right for?

Intermittent fasting is a safe and potentially beneficial method for many, but it is neither necessary nor superior. It works best for people who:

- Want a simple eating system
- Are not naturally breakfast eaters
- Want to reduce snacking
- Are willing to listen to their bodies
- Do not belong to risk groups

Weight management is always individual. If intermittent fasting does not feel right for you, that is completely normal — there are many other ways to reach your goals.

References:
- Welton, S. et al. (2020). Intermittent fasting and weight loss: Systematic review. Canadian Family Physician, 66(2), 117-125.
- Halberg, N. et al. (2005). Effect of intermittent fasting and refeeding on insulin action in healthy men. Journal of Applied Physiology, 99(6), 2128-2136.
- Heilbronn, L.K. et al. (2005). Glucose tolerance and skeletal muscle gene expression in response to alternate day fasting. Obesity Research, 13(3), 574-581.
- Tinsley, G.M. & La Bounty, P.M. (2015). Effects of intermittent fasting on body composition and clinical health markers in humans. Nutrition Reviews, 73(10), 661-674.
- Cioffi, I. et al. (2018). Intermittent versus continuous energy restriction on weight loss and cardiometabolic outcomes. Journal of Translational Medicine, 16(1), 371.

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Last updated: March 15, 2025