Intermittent Fasting For Weight Loss: The Basics
Texas A&M AgriLife Extension Service and Texas A&M College of Agriculture and Life Sciences specialists are weighing in on the diet-craze of intermittent fasting and what this diet could offer long term. While weight loss is the primary perk of intermittent fasting, benefits may also include glucose control and managing risks for cardiovascular disease and cancer.
Jenna Anding, Ph.D., RDN, LD, professor and associate department head for the Department of Nutrition and Food Sciences and AgriLife Extension specialist, and Karen Geismar, RDN, LD, CNSC, senior lecturer and dietetic internship director for Nutrition and Food Sciences, describe intermittent fasting as periods of fasting for one or more days during the week. What it really comes down to, is creating an eating and non-eating window.
Some of the reported benefits of intermittent fasting include improved insulin sensitivity, increased use of body fat for energy, reduced inflammation, improved cognitive brain function, and protection of the brain from neurodegenerative disease, explained Geismar.
The basics of intermittent fasting
“There is no set way to do intermittent fasting,” Anding said. “Some people fast every other day, while others may fast daily for a period of time each day, such as eating during a set number of hours, like between 8 a.m. and 5 p.m. or 11 a.m. and 7 p.m.”
“One of the more popular ways is a 5:2 approach, where you eat how you normally would for five days of the week, but on two non-consecutive days you would fast,” she said.
“The best timing will vary from person to person,” she said, “Someone who is interested in trying this method of weight loss would need to consider his/her physical activity schedule, work schedule, family activities, if they take any medication that requires food, etc. You may also have to schedule fasting around social activities and events that include food and/or beverages.”
Health benefits of intermittent fasting
With such variety in methods for intermittent fasting, it is hard to tell which method, if any, is most beneficial, Geismar noted. A few studies with humans suggest there could be some merit to intermittent fasting.
“Most of the studies on the health benefits of intermittent fasting, other than weight loss, focus on benefits of glucose control, cardiovascular risk factors — i.e. total cholesterol, LDL, HDL, triglycerides — and measured levels of inflammation in the body. All of these are what we call ‘metabolic’ parameters,” Geismar said.
However, most of those studies usually involve a small number of subjects, have not been well-controlled and have not been investigated on a long-term basis. “We consider these as weaknesses of a study, leaving doubt or uncertainty of the validity of the results,” she said.
“There have also been studies investigating the impact of intermittent fasting on cancer and neurodegenerative decline,” she said. “While the preliminary findings look promising, these studies are primarily limited to animal models. We really can’t translate the findings from these studies to humans until we have a large-scale, well-controlled study done on humans.”
Can intermittent fasting be damaging?
Anding noted that it is still unknown whether or not there are physical or psychological benefits or harm to intermittent fasting.
“One thing to consider is that if a person takes certain medications that can lower their blood sugar, then fasting could result in hypoglycemia,” she said. “On the other hand, some types of medication require that they are taken with food to optimize absorption. If this does not occur, then the absorption of the medication may be lessened, and the person will not get the intended benefit.”
People who are interested in intermittent fasting and who take medications should check with their physician and/or pharmacist to make sure there is not a negative impact on their medications during fasting days, Anding advised.
For some people, intermittent fasting may be easier because they only have to watch their calorie intake during fasting times as opposed to following a continuous low-calorie diet.
“They don’t have to think about what they need to eat – they just don’t eat,” Anding said.
Some challenges could arise with intermittent fasting, Geismar said. Things to consider include:
- If you eat more than normal the day before you fast, you may not cut out enough calories to promote weight loss.
- If you don’t have a healthy diet to begin with and you begin fasting, then you may not be getting all the nutrients you need.
- If you are just going without food to help lose weight, is this a way of eating that is sustainable? Without changing eating and lifestyle behaviors, it may be difficult to maintain long-term results.
Maintaining a healthy diet while fasting
“Diet” is often thought about in terms of weight loss, but foods impact many other aspects of our physical and cognitive health.
“We should think about the foods we eat not only to promote a healthy weight but also to prevent chronic disease,” Geismar said. “For example, the DASH, or Dietary Approaches to Stop Hypertension, and the Mediterranean diets have been shown to promote not only a healthy weight but also reduce the risk for diseases such as heart disease and diabetes.”
Anding advised that per the Academy of Nutrition and Dietetics, intermittent fasting is not a recognized treatment for either weight loss or the treatment of disease.
Individuals should still strive to improve their overall eating habits and lifestyle; otherwise, it is uncertain if intermittent fasting will benefit their health and weight loss goals in the long term, she said.
Anyone who is interested in using intermittent fasting for weight loss or the treatment of a chronic disease should check with their physician first and also seek the guidance of a registered dietitian nutritionist.
Who should not do intermittent fasting?
“People with a history of eating disorders, women who are pregnant or lactating, or individuals with diabetes should not use intermittent fasting,” Geismar said. “Also, people who are already not eating enough, perhaps due to illness, should probably not try this diet since it can reduce calories even more.”
“The bottom line, not eating for a period of time or for one or two days out of the week is not going to be beneficial if on the other days and times, you are not eating healthy,” Anding said.
“An overall healthy diet that includes foods from all food groups, like fruits, vegetables, whole grains, dairy, and lean meat, along with a healthy lifestyle, are associated with a healthier body weight and reduced risk of chronic diseases.”