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Interest in dietary strategies for weight loss has increased. Among them, intermittent fasting (IF) draws attention to its possible ability to reduce weight faster. However, is there a clear scientific basis for this effect? That’s what we’re going to find out today.
What Is Intermittent Fasting?
Intermittent fasting (IF) is a dietary approach to prolong the interval between meals.
It is generally used as an umbrella term to define eating patterns in which individuals spend long periods (e.g., 16 to 48 hours ) with little or no energy intake regularly.
What Are The Types Of Intermittent Fasting?
Among the variations of intermittent fasting methods, some described in the literature are:
- Fasting every other day, 1 to 4 days a week, with zero calorie intake;
- Modified alternate-day fasting, with more than 60% energy restriction on fasting days;
- Fast every day, for periods of 14 to 20 hours;
- Fasting (5:2), in which you usually eat five days a week, with intermittent restriction on the remaining two days.
Thus, unlike a traditional restrictive diet, individuals undergoing intermittent fasting do not need to restrict calories daily. Furthermore, the consumption of certain food groups is not “forbidden.”
The central premise is that, during meals, individuals do not fully compensate for the caloric restriction of long break periods. Thus, a negative energy balance is created, resulting in weight loss.
Effect On Weight Loss
Scientific literature suggests intermittent fasting is associated with substantial weight loss over short periods, around 8 to 12 weeks, with a reduction of 0.1 to 0.6 kg per week (or 3 to 8% weight loss since the beginning). Most of the loss is due to the reduction of subcutaneous fat mass.
These results are consequences of metabolic changes caused by the caloric deficit established in fasting, which leads to increased lipolysis, proteolysis, and glycogenolysis depletion.
Intermittent fasting has also been shown to downregulate mTOR gene expression in muscle tissue, which decreases protein synthesis and increases lipid oxidation.
Finally, JI also can lower hormone ghrelin levels, which reduces stimulation of the hypothalamic hunger center.
In addition to rapid weight loss, other benefits of intermittent fasting include the following:
- Lowering blood pressure and heart rate.
- Improving lipid profile.
- Lowering total cholesterol and LDL-c.
- Increasing HDL cholesterol levels.
However, the evidence is conflicting.
Interest in dietary strategies for weight loss has increased. Among them, intermittent fasting (IF) draws attention to its possible ability to reduce weight faster. However, is there a clear scientific basis for this effect? That’s what we’re going to find out today.
What Is Intermittent Fasting?
Intermittent fasting (IF) is a dietary approach to prolong the interval between meals.
It is generally used as an umbrella term to define eating patterns in which individuals spend long periods (e.g., 16 to 48 hours ) with little or no energy intake regularly.
What Are The Types Of Intermittent Fasting?
Among the variations of intermittent fasting methods, some described in the literature are:
- Fasting every other day, 1 to 4 days a week, with zero calorie intake;
- Modified alternate-day fasting, with more than 60% energy restriction on fasting days;
- Fast every day, for periods of 14 to 20 hours;
- Fasting (5:2), in which you usually eat five days a week, with intermittent restriction on the remaining two days.
Thus, unlike a traditional restrictive diet, individuals undergoing intermittent fasting do not need to restrict calories daily. Furthermore, the consumption of certain food groups is not “forbidden.”
The central premise is that, during meals, individuals do not fully compensate for the caloric restriction of long break periods. Thus, a negative energy balance is created, resulting in weight loss.
Effect On Weight Loss
Scientific literature suggests intermittent fasting is associated with substantial weight loss over short periods, around 8 to 12 weeks, with a reduction of 0.1 to 0.6 kg per week (or 3 to 8% weight loss since the beginning). Most of the loss is due to the reduction of subcutaneous fat mass.
These results are consequences of metabolic changes caused by the caloric deficit established in fasting, which leads to increased lipolysis, proteolysis, and glycogenolysis depletion.
Intermittent fasting has also been shown to downregulate mTOR gene expression in muscle tissue, which decreases protein synthesis and increases lipid oxidation.
Finally, JI also can lower hormone ghrelin levels, which reduces stimulation of the hypothalamic hunger center.
In addition to rapid weight loss, other benefits of intermittent fasting include the following:
- Lowering blood pressure and heart rate.
- Improving lipid profile.
- Lowering total cholesterol and LDL-c.
- Increasing HDL cholesterol levels.
However, the evidence is conflicting.
Are These Results Unique To Intermittent Fasting?
Despite the beneficial effects, evidence suggests that intermittent fasting produces weight loss equivalent to that compared to a typical calorie-restricted diet.
In a scientific review of the journal “Nutrients,” in which 11 studies about intermittent fasting and weight loss were analyzed, nine did not show significant differences in body fat loss between the groups that followed the JI and the groups on a diet expected caloric deficit.
Furthermore, in the research that has found some positive differences for intermittent fasting, these differences are only modest.
What Are The Disadvantages Of Intermittent Fasting?
First, anyone cannot practice fasting, being dangerous for patients with type 1 diabetes, pregnant or breastfeeding women, and people with eating disorders.
Furthermore, fasting is not advantageous in the long term: over one year, adherence to this practice tends to drop between 21 and 44%, characterizing a high dropout rate.
Then, a decrease in leptin and adiponectin concentrations is noted in groups under IF. This reduction could be more interesting since adiponectin acts in anti-inflammatory processes and regulates insulin sensitivity, while leptin is responsible for signaling satiety.
Other adverse effects include: decreased muscle mass, menstrual cycle changes, increased weight regain after dieting, decreased micronutrient intake, bad breath, weakness, dizziness, constipation, tension, anger, and fatigue.
After All, Is Intermittent Fasting A Good Weight Loss Strategy?
Intermittent fasting is effective for short-term weight loss and brings possible benefits in the metabolic context.
However, other calorie-restricted diets may find similar results in treating obesity and overweight without the sudden change in routine that fasting imposes. Furthermore, JI may not be effective in the long term and have adverse effects.
In this case, the most appropriate thing is for the nutritionist to carefully assess the best weight loss method to be applied in the context of each patient, considering the health impacts of each intervention, to achieve entirely satisfactory results.
Also Read: Intermittent Fasting: Myths And Truths