For years, we have been bombarded with messages telling us that breakfast is the "most important meal of the day" and that eating every three hours will "speed up your metabolism." If that's true, then fasting and skipping meals must wreak havoc on your metabolism and cause weight gain, right? Maybe not.
Recently, intermittent fasting has gained popularity as new research studies and diet trends emerge. Fasting has been practiced for centuries (usually for religious regions), but is there a benefit to intermittent fasting and time-restricted feeding (that is, consuming energy intake within a specific time window each day)? The short answer: probably.
Keep in mind there are currently only two trials in human beings that look at time-restricted feeding interventions, so more research is warranted. With that said, the results are promising. Both of the trials found significant reduction in weight from this type of eating pattern, while one study even saw reductions in fasting blood glucose and improvements in LDL and HDL cholesterol levels.
Key takeaways from three pieces of research include:
- The fasting occurred daily for at least 11 hours between 7 p.m. and 6 a.m. in one study and was given as one meal (with comparison group eating three square meals) in another study. So, although recent diet trends recommend a 16-hour fast with eight hours of eating, there are still inadequate data to determine the ideal fasting period.
- Research in animals suggests that intermittent fasting not only can reduce obesity but also can reduce chronic diseases such as diabetes and cancer, and conditions such as nonalcoholic fatty liver disease.
- Opponents of intermittent fasting state that periods of fasting lead to periods of overeating. However, this is not clear and has not been proven.
- Data are lacking regarding the effects of intermittent fasting on other health behaviors such as diet quality, sleep and physical activity — all important factors in overall health.
Should You Try Intermittent Fasting?
While this summary discusses intermittent fasting as a promising approach for weight loss and metabolic health, as a registered dietitian nutritionist, I would not recommend it to everyone. People who are underweight, have a history of eating disorders, people with diabetes or problems with blood sugar control, people with any medical condition and people taking medications should never fast without consulting with a doctor first.
Also, currently, intermittent fasting does seem to be more of a trend than a sustainable way of eating. And the best eating pattern will always be one that you can create a lifestyle around and that you enjoy. If you're reading this information and aren't sure how this fits into your lifestyle, work with an RDN to create a successful nutrition plan tailored to you.