The Pros and Cons of Intermittent Fasting

In recent years, Intermittent fasting (IF) regimens have become very popular. Some people find that this weight loss approach is easier to adhere to than traditional diets involving calorie restriction. In general, IF involves restricting food intake on certain days each week or certain times of the day and eating as you please on the non-restricted days/times. Here’s an overview of some of the subsets of IF.

Intermittent Fasting: Alternate Day Fasting

Emphasis: Rotating days of eating and days of fasting. No foods/beverages with calories are consumed on fasting days, but you may consume calorie-free drinks (e.g. water, black coffee, tea). One can eat whatever they choose on eating days, although it is recommended to eat according to healthy eating guidelines. The idea is that over the course of a week, the total number of calories an individual typically consumes would be less. Therefore, over time one would lose weight by eating fewer calories.

Evidence: According to eatright.org, the amount of weight loss following this alternate-day fast was equal to that lost after following a typical low-calorie weight loss plan. This is a difficult fasting pattern with side effects such as serious hunger pangs and decreased concentration on days when fasting occurs. Some studies also resulted in individuals eating more than usual on eating days, therefore not enough calories were restricted to promote weight loss. Long-term effects on personal health of this fasting pattern are also still unknown, so more research is needed on this IF subset as an approach to weight loss.

Intermittent Fasting: Modified Fasting

Emphasis: Eating very little amounts of food on fasting days (i.e. 20-25% of needed calories). Other plans limit intake to only 500 calories on fasting days and the 5:2 fast calls for fasting two days/week while following a usual eating pattern on the other 5 days.

Evidence: There is contradictory evidence for this subset of IF. Some following modified fasting lost more weight compared to those on a traditional weight loss diet (calorie restriction), although the difference was not significant. Other studies found no difference in weight loss. Not enough research has been done to know if this dietary pattern is a safe/effective method to lose weight and keep it off.

Intermittent Fasting: Time-Restricted Fasting

Emphasis: This limits your food intake to a certain number of hours each day. For example, you may choose to eat all your food for the day in an 8-hour period, such as 10 a.m. to 6 p.m. Thus, the remaining 16 hours each day are the fasting period and no calories are consumed during this time. You then repeat this same schedule every day. For some individuals, this will help reduce the number of calories they eat in a day which can produce weight loss over time. However, if you consume higher-calorie foods with time-restricted eating, then you may not end up eating less or notice a drop in weight.

Evidence: According to eatright.org, the effectiveness of this subset of IF for weight loss is still unknown. Most studies have only been done with lab animals, therefore there are very few results from studies done with humans. Research is also limited in regards to how time-restricted eating benefits heart health and blood sugar.

Intermittent Fasting: Overview

Claims: IF may pose a health risk for certain populations, therefore it is not recommended for those with diabetes, pregnant women or those breastfeeding, and anyone with a history of eating disorders or disordered eating. Currently, research is being done in relation to fasting and longevity, cancer, neurological diseases, autoimmune and metabolic disease. It is hypothesized that fasting can activate cellular mechanisms that help boost immune function and reduce inflammation. While there is not robust enough evidence to currently recommend IF for weight loss, there may be disease states where it is more helpful for than just weight loss. It’s always best for anyone considering IF to discuss this with a doctor first, especially If they are taking medications that need to be adjusted accordingly.

Evidence: IF is not a current recommendation for weight loss or other health conditions. More research is needed on this treatment (i.e. negative side effects of fasting associated with nutrient deficiencies). Much of the research comes from studies on small groups of people or is only limited to animal studies. Therefore, the results may not be applicable to the general population and the long-term effects of IF are unknown.

Athens Nutrition Opinion: Although we do recommend limiting late-night eating, eating when you are hungry and most active, IF seems to be another form of dieting. The additional restrictions may ultimately cause individuals to override their natural signals of hunger and satiety. Over time, these eating restrictions may backfire and unhealthy weight cycling will start again. At Athens Nutrition, we individualize your eating plan, focusing on your lifestyle, your eating and cooking preferences, your work, home and family schedules, and your health goals so we can create a plan that works for you.