While intermittent fasting seems like the new “thing” in weight-loss, fasting has always been around. We technically fast every time we go to sleep (since we go several hours without eating) and the term “break-fast” comes from the idea of breaking this overnight fast.
Many would associate the idea of fasting with starvation, but this is not the case. Fasting refers to not eating for longer than usual, while starvation refers to extreme hunger and malnourishment. Thinking of fasting in terms of starvation can make it seem more extreme than it actually is and lead to it being dismissed as just another fad.
In fact, plenty of animal studies seem to support the idea of fasting for weight loss and for improving metabolic profiles like blood cholesterol levels and insulin sensitivity. Fasting studies in humans are still preliminary, however, but research does suggest health benefits from fasting.
What Is Intermittent Fasting?
Intermittent fasting (IF) is technically not a diet, but a feeding schedule or pattern. This technique sets up times or days in which we can eat and does not allow eating or snacking otherwise. The idea is to use stored energy (fat) for fuel rather than to make more.
There are many types of intermittent fasting including alternate day fasting including the 5:2 method, alternate-day fasting, and time-restricted eating.
5:2 Method. This method involves fasting for two days out of the week (and a healthy diet for five). Depending on who you ask, this type of fasting might completely cut out eating or allow ~ 200 calories on fasting days.
Alternate Day Fasting. As it sounds this method involves fasting every other day, it may completely restrict calories or allow ~500 calories on fasting days.
Time-restricted eating. Also known as the 16/8 or 14/10 method, referring to fasting hours and eating hours in a 24-hour day cycle. A person might fast for 16 hours and eat for 8 or fast for 14 hours and eat for 10. This is a popular approach since it can be partly done overnight and by skipping breakfast.
No single method has been found to be significantly better than others, but some may be easier to undertake. For example, most would find it easier to do time-restricted eating (where we fast for several hours) than alternate day fasting (where we fast for entire days). Which method works best may depend on which best fits the individual lifestyle or schedule.
How it Works
Usually, the time period between meals allows for insulin and blood sugar levels to drop and for cells to use up stored energy. When food is reintroduced, insulin and blood sugar levels rise again and cells take in sugar to store it as glycogen and fat. Fasting allows insulin and sugar levels to remain low enough for long enough such that the body burns stored energy (fat).
Energy balance (calories in versus calories out) also plays a role in weight-loss with IF. During fasting, few to no calories are introduced to the body but are still burned to maintain function. This creates a negative energy balance, meaning that we are burning more calories than we are consuming, which is ideal for weight-loss.
Breaking the fast usually focuses on calories quality and involves a well-balanced diet rich in protein and fiber. This helps prevent nutritional deficiencies is necessary for a successful outcome. If someone fasts, but pigs out on chips and cookies on non-fasting days then successful weight-loss in unlikely.
Potential Health Benefits
While research on fasting does suggest a lot of benefits, these are mostly in animal models. Fasting in animal models show improvements in blood sugar, cholesterol, blood pressure, insulin sensitivity, and fat mass. These improvements would positively benefit the incidence of chronic disease (like diabetes and cardiovascular disease) in humans but more data is needed.
Research on humans is rather scarce but highly suggestive. Most studies suggest there may be a benefit to fasting including a loss in fat mass and increased insulin sensitivity. Definite improvements in blood pressure and blood lipid levels are still too early to claim.
Is it Better than Other Weight-loss Methods?
According to experts at the Harvard School of Public Health intermittent fasting is no better than any other well-balanced diet and exercise program. If done correctly, it will result in weight-loss but most of these effects are short-term and easily reversible if not sustained.
While I.F. might help somewhat, it is still important to have a healthy and balanced diet rich in plant fibers and nutrients to maintain a healthy weight. Do your homework before undertaking any new diet regimen and ask questions if confused. Help from a nutritionist or physician can ensure that attempts at IF are manageable and safe.
- Horne, et al. “Health Effects of Intermittent Fasting: Hormesis or Harm? A Systematic Review.” OUP Academic, Oxford University Press, 1 July 2015, academic.oup.com/ajcn/article/102/2/464/4564588.
- Varady, Krista A, and Marc K Hellerstein. Alternate-Day Fasting and Chronic Disease Prevention: a …www.ncbi.nlm.nih.gov/pubmed/17616757.
- Tello, Monique. “Intermittent Fasting: Surprising Update.” Harvard Health Blog, 26 June 2018, www.health.harvard.edu/blog/intermittent-fasting-surprising-update-2018062914156.