Intermittent Fasting Vs. Calorie Restricted Diet- Which is better for Health?
Katie Gurnee1, Victoria Ling JN2
1. 18166296@studentmail.ul.ie 2. 18106439@studentmail.ul.ie
Abstract: Intermittent Fasting and Calorie Restriction are both common methods for weight loss and weight management. In our research, we wanted to discover the differences that these two diets can have in our bodies and overall health. We found that Intermittent Fasting in particular had huge impacts on insulin sensitivity and insulin levels as well as lowering blood pressure and diversifying gut biomes. This was all whilst maintaining muscle mass and not increasing hunger. We have also noted how Intermittent Fasting may not be suitable for all women due to the unusual effect it can have on hormones. Several lines of evidence have also shown that Calorie Restriction slows down metabolism and decrease physical activity in the subjects using it but also has extensively been proven to increase lifespan in several different species.
1. Introduction:
A major global health concern as of now is the issue of obesity, due to the abundance of processed food and sedentary lifestyle. With this comes obesity related diseases such as Type-2 Diabetes, cardiovascular diseases and more. Intermittent Fasting (IF) and Calorie Restriction (CR) are more to health than just methods to lose weight. To maintain weight everyone has a total daily energy expenditure that takes in to account your basal metabolic rate and your physical activities. For any individual that are looking to lose weight there would need to be a deficit of 3,500 calories per lb. (7,700 calories per kg). Intermittent Fasting is an eating pattern where you cycle between eating and fasting. There are several ways that are accepted to do this that include eating for a set number of consecutive hours a day and then fasting for most of the day or fasting for a few days a week and then eating for the majority. Calorie restriction is a diet that restricts a person to a limited number of calories per day, usually 10~15% percent lesser than the recommended calorie intake. We will be exploring the pros and cons of both diets.
2. Results:
Intermittent fasting (IF) has become increasingly popular as a simple means of controlling weight. IF boasts a lot of health benefits, promoting weight loss without decreasing muscle mass, as well as improving metabolic health (Fontana and Partridge, 2015; Gotthardt et al., 2016; Mattson and Wan, 2005; Patterson and Sears, 2017). Studies conducted by the University of Alabama showed that with an IF diet, a group of prediabetic males appears to have improved insulin sensitivity and largely decreased insulin levels as well as lowered blood pressure(Sutton et al., 2018). It has also shown to decrease insulin levels in healthy males (Halberg et al., 2005).
Furthermore, fasting stimulates the growth of complex and diverse gut microbiome, which influences net energy absorption, expenditure and storage as well as improve host metabolism (Ekmekcioglu and Touitou, 2011; Goodrich et al., 2014; Li et al., 2017). Despite not eating for a long period of time, subjects in studies did not feel extreme hunger, as IF normalizes Leptin and Ghrelin, and therefore feel less hungry as well as have a lower appetite level due to Ghrelin adapting to their body’s eating schedule (Natalucci et al., 2005). Another thing to note is that cholesterol level, especially LDL, decreased after 6 months. However, during the diet period, cholesterol levels were elevated(Sävendahl and Underwood, 1999), though this is not alarming, as rapid weight loss can cause an increase in apolipoprotein B and LDL-cholesterol levels, and similar cases were also shown in ketogenic diets as well as Mediterranean diets (Sharman et al., 2002). IF also shows promising results as well in reducing the risk of type-2 diabetes in the obese population (Arnason et al., 2017; Barnosky et al., 2014).
However, when it comes to intermittent fasting, the fact that women have more kisspeptin makes them more sensitive to the diet than men. If the diet is not done properly, it could easily disrupt their cycle and throw off their hormones (Hoyenga and Hoyenga, 1982; Martin et al., 2007). Therefore, females that are pregnant, breastfeeding of trying to conceive, as well as those with fertility problems or a history of amenorrhea could easily be affected by IF. In another randomized controlled trial, constipation was reported, but soon resolved after test subjects were recommended to eat vegetables and fruits (Varady et al., 2013). In the same trial, 13% of subjects reported having headaches, though the cause is unknown.
Calorie restriction has always been a well-known method of weight loss and perhaps the most widely used. However, studies show that metabolic rate slows when you cut your calorie intake dramatically. This allowed less calories to be burned by the subjects as our bodies try and preserve our stores. The same study also showed that subjects on a restricted diet decreased their physical activity levels, dramatically lowering their total daily energy expenditure (Redman, L. M., Heilbronn, L. K., Martin, C. K., de Jonge, L., Williamson, D. A., Delany, J. P., Ravussin, E., Pennington CALERIE Team 2009). For most people this is the opposite effect that would aim for since they would consistently have to eat less as their metabolism slows.
Although the metabolic rate slows there are many studies showing that maintaining a lower calorie diet is extremely healthy if done properly and can even extend lifespan. This has been proven on rats, mice, fish, flies, worms and yeast (Leonie K Heilbronn, Eric Ravussin; 2003). SIR2 and SIRT1 are genes closely linked to longevity and cellular regulation. Research done on these genes have shown that a calorie restricted diet increases and activates them allowing us to survive longer(Wang, 2014). The diet can also reduce oxidative stress and inflammation in adults (Johnson et al., 2007). Furthermore, calorie restriction significantly reduces the risk of cardiovascular diseases (Lefevre et al., 2009).
3. Discussion:
Overall, evidence suggests that the IF diet is a promising approach to weight loss for both obese and healthy adults and contributes to their metabolic profiles. However, though most intermittent fasting regimen results in weight loss, the numbers appear to be statistically similar to that of a CR diet, suggesting that in terms of efficiency, both are suitable for an individual whose end goal is to lose weight. Most research done in this area were performed on rats, primates and other mammals, and might not apply to a human. Data, as well, were lacking regarding the impacts of IF and CR diets on several other health behaviours.