People have observed periods of fasting in cultural and religious practices for thousands of years. However, intermittent fasting (IF) has gained traction in recent years-with proponents touting benefits galore. Does IF truly stand the test of time from a health standpoint or should it remain a spiritual sacrament?
Intermittent fasting involves a period of calorie avoidance in varying length. Some protocols suggest simply evading calories for the majority of the day by selecting an eight-hour ‘eating window’ with a 16-hour fast. Others suggest extending the length of the fast or adopting extreme calorie restriction on multiple, non-consecutive days each week. When compared with other diet types, IF may be a more approachable diet for many because it only requires limited intake during these specified time frames- rather than restricting all foods or specific foods all of the time. In fact, during the eating window of IF there are no stipulations on amounts or types of foods that may be eaten. During the fasting window of IF non-caloric beverages such as water, unsweetened tea, or black coffee are acceptable. Not only is IF potentially an easier approach versus classic dieting, research on the subject shows some pretty exciting results when it comes to human health & longevity.
Intermittent fasting shows significant decreases in body weight, fat mass, and weight circumference in human studies. These results are unsurprising since we know that fasters tend to end up in a negative calorie balance at the end of an IF day- meaning that they rarely eat enough during the eating window to make up for the calorie restriction in the fasted window. For this reason it is still unclear whether the weight loss produced is a function of fasting itself or whether it is actually resulting from the overall calorie restriction. Regardless- if IF is more approachable for you compared to classic models of dieting, it may be an effective option to achieve weight loss and improve body composition.
Studies suggest that IF improves insulin sensitivity and blood sugar regulation to a greater degree than other types of caloric restriction. Intermittent fasting has also shown positive results related to oxidative stress and inflammation. All of these outcomes have profound implications for human longevity since each have their own relation to mortality.
Aside from the physical benefits of fasting, cognitive performance improvements have also been found in human IF research. Intermittent fasting results in metabolic changes that may protect memory and learning functionality as well as slow progression of diseases in the brain.
Feeling inspired to begin IF? Here are some considerations for anyone who is thinking about adopting this eating pattern:
Athletes should be particularly mindful during IF. While many active people do adopt a lifestyle of IF without negative performance outcomes, there’s little research on elite athletes (especially in endurance sports) practicing this model. Considerations in the athletic population include achieving adequate fuel for training and recovery as well during events.
A potential consequence in IF is an unintended encouragement of extreme eating behaviors- such as bingeing or anorexia. It is not recommended for individuals who have tendencies towards disordered eating patterns to begin IF protocols. In order to maintain a healthy relationship with your body’s natural hunger cues- I recommend choosing the IF version suggesting a daily time restricted eating schedule by fasting 16 hours daily; rather than extending the fast for longer periods.
Regardless of whether we’ve intentionally fasted in the past or not- we’ve all gone hours without eating at some point in time. A classic outcome: our hunger turns into irritability, we become ‘hangry’. This reaction is to be expected, especially when we aren’t used to fasting. Most IF proponents claim that, after a couple of weeks, this cantankerous attitude during fasts subsides and that they actually have fewer food cravings and hunger pangs.
Without realizing it, we get a lot of our daily fluids from the foods that we eat throughout the day. It is important to make sure that you are drinking plenty of non-caloric beverages during your fasts to avoid dehydration- water is best.
While no foods are off limits when in the eating window of IF- I think we can all agree that loading up on masses of food like burgers, fries, and cake is never the best option. Instead, continue to eat sensibly and choose healthy foods like vegetables, legumes, fruits, whole grains, lean proteins, and healthy fats the majority of the time and (sure!) indulge on occasion.