With the holidays upon us and everyone focused on watching their waistline, it’s a natural to think about the ideal diet to prevent weight gain and maybe even promote weight a little loss.

Let’s face it, it’s really difficult to go on a “diet”. Diets are faced with a high risk of failure with the bulk of them failing, ending with eventual weight gain above and beyond where you started.

The concept of caloric restriction which has been explored as a way to improve longevity has been shown to be successful in animal models (mice), offering an enticing possibility to humans. But implementing this into your daily lifestyle may be problematic and may not be realistic in the long run.

Another more intriguing approach that has been gaining popularity in the past decade is intermittent fasting (IF), a form of time-restricted eating.

In a nutshell, it’s a way to extend the window of time during the day in which you don’t eat. Instead of eating from the time you awaken, the goal is to delay the onset of eating, thereby extending your fasting period that naturally occurs when you sleep.

IF involves only eating for a defined period of time in a 24-hour period. For example, it may involve eating for an 8-hour period during the day—as opposed to grazing on food all day long—and fasting for the remaining 16 hours. (During the fast, you are permitted to drink water, have black coffee, or tea.) 

For example, instead of eating from 7 am when you awaken, you would begin eating at 11 am or noon until 7 or 8 pm. When you do eat, the goal is to eat moderately, although you are permitted to eat the foods that you would normally eat.

Variations on this theme include the 5:2 approach (eating normally 5 days a week and approximately 500-600 calories 2 days week), or alternate day fasting (ADF).

With IF becoming more popular, it’s important that physicians and other healthcare professionals be aware of the principles and science behind the diet in order to have a rational discussion with their patients.

In an article published today in the New England Journal of Medicine, Mark Mattson, PhD, a neuroscientist at Johns Hopkins School of Medicine, explains the nuances behind the approach to IF, along with why he adopted this approach to eating more than 20 years ago.

Mattson’s personal reasons for adopting intermittent fasting  began well before he embarked research into the topic itself. It actually began about 35-40 years ago as a method he could use to reduce symptoms related to acid reflux which he found were worse if he ate breakfast and then rode his bike to work in the research lab.

“I started doing it way back in graduate school at the University of Iowa in the early 80s,” he explained. “So I quit eating breakfast and found that I didn’t get the reflux—and I haven’t eaten breakfast since then!”

Little did he realize that this was at the beginning of a pursuit of a concept that would shape his research, and have broad implications for disease management, metabolism as well as weight loss.

Health Benefits of Intermittent Fasting

While certain subgroups of patients, including those with diabetes and pre-diabetes may benefit from adopting this approach to eating (by lowering HB A1C levels), its value and principles certainly extends to other subgroups including those with cardiovascular disease, neurologic ailments (multiple sclerosis, Alzheimer’s and Parkinson’s disease) and patients with cancer.

While IF may facilitate weight loss by reduced caloric intake, its more important benefits include improved glucose regulation via lower insulin levels, reduced blood pressure and lower resting heart rate, all indicators of improved health.

There may also be a reduction in weight-related medical conditions such as elevated cholesterol, and non-alcoholic fatty liver disease (NAFLD), offered Dr. Minisha Sood, an endocrinologist at Lenox Hill Hospital, in New York City.

“Importantly, intermittent fasting or alignment of eating with our natural circadian rhythms may positively impact the gut microbiome which could improve overall metabolism and health,” she explained. 

Metabolic Switching

The concept by which this is facilitated is known as “metabolic switching”, which according to Mattson, is a healthy homeostatic mechanism that evolved in Homo Sapiens over thousands of years during periods when food was scarce. This involves switching by our body’s cells from using glucose during the fed state to free fatty acids (FFA) and ketone bodies during periods of starvation. This switch, which is metabolically advantageous, actually serves to reduce inflammation by utilizing adaptive pathways in our cellular machinery.

As Mattson explains, glucose is the normal fuel our bodies rely on during the “fed” state. When we eat, excess glucose beyond immediate caloric expenditures is stored as a compound known as glycogen in the liver for quick burst of energy, but excess as fats (triglycerides). Triglycerides or fat is broken down to compounds known as “free fatty acids” (FFA) along with glycerol. Further metabolism of FFA by the body produces compounds known as “ketone bodies” which are used by the brain, heart and other organs during periods when glucose is not immediately available.

Clearly IF is not for everyone, with lifestyle, age, medical history, work hours (shifts) and personal preference being key factors that may influence the ability to adhere to this lifestyle and approach to eating, as Mattson explains. There may also be sex differences and genetics that ultimately influence individual success with IF.

“Time restricted eating or intermittent fasting may be actually easier to stick with than daily calorie restriction or daily calorie control,” explained Sood. When studied head-to-head, intermittent fasting and daily calorie restriction are both equally effective for weight loss so it’s really a matter of finding an approach which works with one’s lifestyle and which can be followed consistently.”

In regard to potential downsides of IF, Sood explained that “some people may experience increased hunger toward the end of the fasting period each day—the hunger response may wane over time and people adjust. If they do not feel an improvement in hunger levels or they experience headache or fatigue while fasting they may want to consider a shorter fast or an alternative approach to weight loss.”

Health coaches and fitness professionals also have seen encouraging results in terms of improved stamina and muscle strengthening after integrating IF into workouts and training sessions for clients.

“I’ve seen clients drop 1-2 lbs per week, making no changes to their diet at the start—only changing the time that they eat,” said Nicole Winhoffer, a fitness artist, and creator of the NW Method in New York City. “Their brains functioned better, they performed better, and were able to execute 30% more in their workouts.”

Elite athletes have also embraced this concept, according to Mattson. “It’s clear that British athletes have excelled in the Tour de France in the last 5-7 years,” he offered. The potential reason? The use of keto esther, a supplement which Mattson points out has surged in popularity among elite British cyclists in recent years. The World Anti-Doping Agency (WADA), he explained, has cleared this compound since it is naturally derived. The results have been rather impressive to say the least.

 Intermittent Fasting to Treat Chronic Disease

Buy there are several areas where Mattson believes that IF may have positive benefits including cancer and neurologic diseases such as multiple sclerosis (MS) Parkinson’s, and Alzheimer’s disease .

He points out various studies where improvement in tumor burden may be seen. His rationale for this approach is based on the premise that cancer cells can only use glucose to proliferate. With IF, with only ketone bodies available, the cells are unable to survive and the tumor burden is reduced.

Research also supports the numerous beneficial metabolic effects of IF related to neurologic function, including positive effects on verbal and working memory and cognition seen in older adults. The benefits further extend to disease states such as MS where ongoing trials hope to show improved function based on preliminary results seen thus far.

“Mattson’s article is an important contribution to our understanding of metabolism. It demonstrates that beyond choosing healthy diets and avoiding high sugar/high fat and processed food, the amount of time between meals can provide significant benefits as well,” offers Benjamin Hirsh, M.D., Director, Preventive Cardiology, Northwell Health's Sandra Atlas Bass Heart Hospital, Manhasset, New York.

“Physician and public health guidance on how to implement healthy lifestyle choices overall will yield much greater benefits overall to individuals hoping to improve their health and the population at large, he explained. “However, for the individual who wants to try a diet where the pattern is as much about fasting as it is about food intake choices, there is now a dietary pattern that they can pursue.” 

“However, this also must be done under the guidance of a physician very knowledgeable about this science, and the diet must be followed very strictly, which will be difficult to do outside the context of a clinical trial,” he added.

Breakfast As The Least Likely Meal

Mattson sums his thoughts about IF up by stating that “from an evolutionary perspective, breakfast is the least likely meal”, a reflection of his thoughts that embrace cellular adaptations and metabolic switching as products of evolution of human physiology. Mattson explains that we never awoke to a “ready-made” breakfast over ten thousand years ago, prior to the agricultural revolution.

Instead, humans had to forage or find food, or make a “kill”. It involved work and time with the natural process of fasting already part of our existence before we could ever eat.

He also envisions how this approach could one day be adopted as part of an approach or treatment for obesity, to help jumpstart the process with inpatient stay, ideally reimbursed by insurance companies or other third party payers. Since we already treat alcohol use disorder and opiate abuse in this manner, why not obesity? The concept is compelling to say the least.