Intermittent Fasting - The New Diet?
Diet trends come and go. And there is now a new one; intermittent fasting. It has become relatively popular; in fact, you will find several hundred thousand hits on a simple internet search. What is this all about?
The idea is that we restrict our caloric intake to a certain time period and fast the remaining time. The temporary hunger you feel may actually be good for you; really? The majority of data supporting this diet comes from studies of male rodent models. Human studies have been limited.
In the context of intermittent fasting, there are at least 3 different types:
Alternate-Day Fasting: alternating fasting days (no calories consumed) and feeding days (no caloric restriction). The data suggest there was a decrease in cholesterol and triglycerides, and reduced fatty liver and inflammatory gene expression, and modest weight loss.
Modified fasting regimens: Here there is severe limited caloric intake instead of no caloric intake. Caloric consumption is limited to 20-25% of energy needs on scheduled fasting days. Data suggest this style of fasting results in weight loss, with modest to mixed effects on lipids and inflammatory markers.
Time-restricted feeding: The most common practice of time-restricted feeding is eating only 8 hours in a 24-hour period (16 hours of fasting). Again, there are limited clinical studies and the data is mixed, but it does suggest a reduction in the risk of obesity and obesity-related conditions (such as nonalcoholic fatty liver), diabetes and cancer.
Overall, there is evidence to support that intermittent fasting is not harmful physically or mentally in healthy adults. The health benefits include weight loss, protection against chronic disease, increased longevity and possibly improved brain function.
So why does this help improve my health? It is hypothesized to influence your bodies function by improving your 1) circadian biology (your sleep/wake cycle), 2) the gut microbiome (the normal bacteria in your gut, which is becoming better understood as important to good health) and 3) modifiable lifestyle behaviors. Furthermore, insulin resistance (what occurs when the cells in your body don’t respond to insulin (which normally cause cells to take in sugar) resulting in increased blood sugar (hyperglycemia)) is also improved. The causes of insulin resistance include obesity, high-calorie/high-sugar diet, lack of physical activity, high dose oral steroids, and chronic stress or other diseases (such as Cushing’s).
Recommendations for weight loss are not short. There are many. Most advise to eat regular meals in order to avoid hunger. However, intermittent fasting may actually have beneficial physiological effects and does not necessarily lead to overeating. This approach to dieting is more of a lifestyle choice and less of a way to just lose weight.
Dr Robert Dean
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