The Average Person and Intermittent Fasting
Considerable research has investigated how restricting calories could have significant health benefits for people with a healthy weight. Intermittent fasting may be an easier way to achieve weight loss and these health benefits.
Intermittent fasting involves various approaches, including periods of non-fasting and fasting. These include alternate-day fasting (one day non-fasting, next day fasting), the 5:2 method (regular eating for five days and fasting for two), and many others.
The article “Alternate-day fasting in nonobese subjects: effects on body weight, body composition, and energy metabolism” [1] studied whether alternate-day fasting is an effective method of losing weight in non-obese people and whether there is evidence that it could increase longevity [1].
The Study.
The study involved normal-weighted subjects, consisting of eight men and eight women aged 23–53 years [1]. The subjects varied in physical activity, with seven being inactive, three exercising 1-2 times a week, and six exercising 4-5 times a week [1].
Competitive athletes and people diagnosed with type 2 diabetes were purposely excluded [1]. These volunteers conducted alternate-day fasting for 22 days, consuming energy-free beverages such as tea, coffee, and sugar-free gum on fasting days and freely eating on non-fasting days [1].
Subjects completed scores multiple times a day to assess feelings of hunger, fullness, desire to eat, satisfaction, and desire to eat food in the future [1].
Measurements such as glucose, free fatty acids, -hydroxybutyrate (an energy source), insulin, and ghrelin (signals when the body needs food) were collected [1].
Additionally, various health measurements were gathered, including oral temperature, blood pressure, fasting blood samples, resting metabolic rate, and body composition (weight, fat, etc.) [1]. Two consecutive days before the experiment, they conducted a 12-hour overnight fast, as well as on the second last day [1]. On the final day, subjects conducted a 36-hour fast [1]. On the same days, the subjects reported to the clinical research centre [1].
The Results.
The results found that subjects lost about 2–3% of their body weight [1], along with significant decreases in fat mass (fat tissue in the body) and fat-free mass (body weight minus fat tissue) [1].
Only half of the subjects completed the survey every day [1]; thus, only 50% of the subjects’ answers were consistent and daily, affecting the validity, reliability, and accuracy of these results. At the beginning of the experiment, there were significant increases in hunger and a decrease in the feeling of fullness [1]. However, these feelings, including thirst, desire to eat, and satisfaction, did not change throughout the experiment [1]. Only the feeling of fullness increased slightly over time [1].
Oral temperature and resting metabolic rate were not affected during this period [1]. However, women had significantly lower glucose, insulin, free fatty acid, triacylglycerol (a main fat component), LDL-cholesterol concentrations, and higher HDL-cholesterol and ghrelin concentrations than men [1]. There were no significant changes in fasting glucose or systolic or diastolic blood pressure [1]. HDL (which carries cholesterol) only increased in women [1], and triacylglycerol was significantly decreased only in men [1].
These measurements seem to indicate that the alternate-day fasting led to decreased cardiovascular risk in women compared to men. Furthermore, the decrease in triacylglycerol could mean that the male subjects decreased the fat consumed in their diets.
Potential Side Effects.
Some of the reported side effects included one subject reporting feeling lightheaded once [1] and four people reporting constipation [1], along with many saying they felt irritable during their fasting days [1]. It is believed that if subjects consume a small meal [1] or higher-protein food on fasting days (which makes people feel fuller), it would potentially lower irritability and hunger, thus hypothetically making people less irritable [1].
The decrease in weight meant that the subjects could not consume enough food on feasting days to maintain their body weight [1]. However, it is hypothesised that those who are bigger eaters will be able to maintain their body weight [1].
Could Intermittent Fasting Make Us Live Longer?
The potential for increased lifespan in humans due to this method is due to results seen in rats [1], where their longevity increases when their fasting glucose and fasting insulin decrease [1]. A decrease in fasting insulin has also been associated with longevity in humans [1].
Study Limitations.
It is acknowledged that results may have been affected by the study design, as the subjects reported eating more than they usually do on the last day, as they knew they were about to do a longer-than-usual fast [1]. Fax oxidation did not increase; however, this result could have been affected as subjects did not consume regular diets [1]. Subjects with a greater ability to oxidise fat also could have lost more weight [1], therefore displaying how different people may be impacted by the fasting method and illustrating how it can differ for each individual due to their genetics and potential lifestyle, including a healthy or unhealthy diet.
Does it Work?
This study displayed the potential benefits of intermittent fasting methods, particularly alternate-day fasting, in providing a doable and alternate method to calorie restrictions regarding losing weight and increasing life span for non-obese people [1], even with some of the study’s limitations. Nevertheless, it provides intrigue as to what this diet could provide regarding health benefits for various people.
A reminder that it is NOT MEDICAL ADVICE and that people must consult with their doctor before making any drastic changes to their diet. These methods do not affect or suit everyone the same; thus, it is always important to consider your case.
References
Reference paper “Alternate-day fasting in nonobese subjects: effects on body weight, body composition, and energy metabolism”.