My personal experiences with both methods, primarily on a short-term basis during my competition prep cutting phases, have been successful. I was using clean flexible feasting that fit my macros, coupled with periods of daily intermittent fasting,
I attribute my success with these protocols only to the fact that I practiced each lifestyle modality based upon my individual personal goals, and lead an active and disciplined lifestyle in terms of my daily food choices. However, intermittent fasting is not a lifestyle choice that is a good fit for everyone. For some, abstaining from eating or drinking a beverage with calories throughout a specified period of the day can be more of a challenge than basic daily caloric restriction (CR) using clean flexible dieting and macro counting.
The current available research on intermittent fasting is reviewed in this article. It expressively outlines the facts. Keep them in mind when deciding if the intermittent fasting lifestyle is for you.
The intermittent fasting lifestyle is not intended to be a form of starvation diet. With the plethora of diet gurus with consumer books on the market boasting various types and ways of fasting and "fasting diets" it's difficult to navigate the intermittent fasting waters at times. Some of these manuscripts promote the avoidance of any calories for an entire day, one or two days a week. Others encourage unhealthy behaviors such as binging once or twice a week.
It is important to keep a level head. Consider what is realistic physiologic stability versus what is considered marketable extremism.
The following is an unbiased overview of what some of the current research. Intermittent fasting has its roots in a religious lifestyle practice called Ramadan fasting. Understand this before hopping on the current fitness industry intermittent fasting ferris wheel.
Traditional Ramadan fasting involves a period of daily fasting from eleven to eighteen hours a day, essentially from sunrise to sunset. This is followed by a large meal at sunset and a smaller meal just before sunrise with minimal physical activity or sleep for a period of twenty to thirty days. 
#1 - Use intermittent fasting if it fits your fitness goalsIf weight loss is part of your overall fitness goals, there is supporting data that short-term implementation of intermittent fasting will aid with a small degree of fat loss. However, data supporting maintenance of lean muscle or fat-free mass is conflicting. 
In a study examining the short-term effects of Ramadan intermittent fasting on body weight and composition, and its potential age and sex-related differences over a period of twenty days, it was concluded that while the traditional method of Ramadan fasting did result in overall weight reduction, fat-free mass was also reduced.
Fat mass declined the most in males of both age groups, and was evaluated at a rate of 2.5% on average from baseline. The younger females experienced a much smaller reduction of 2.3% from baseline, with the females thirty-five and up experienced the least significant reduction in fat mass. Overall, all groups experienced some degree of fat-free mass reduction. 
If weight loss is a goal, there is supporting data that short-term implementation of intermittent fasting will aid with a degree of fat loss.In terms of lean mass maintenance, there are numerous studies that support the consumption of foods and supplements to reduce exercise-induced lean mass damage and loss. However, this concept is also noteworthy in the practice of intermittent fasting, as many prior studies have reported that a primary benefit of intermittent fasting and/or calorie reduction is decreasing of inflammation and oxidative stress, or the body's ability to repair itself after physiologic stress.
A study compared indicators of exercise-induced muscle damage among twenty-nine upper body untrained young adults averaging 22 years of age, twelve of which were female. They either completed an eight hour water-only fast or consumed a controlled diet for eight hours before engaging in a lab-monitored afternoon training session. The results suggested that intermittent fasting does not significantly inhibit markers of exercise-induced muscle damage, but in general affects indirect markers of muscle damage. This supports previous data which claimed reduction of oxidative stress. 
I personally address lean mass maintenance while practicing intermittent fasting through supplementation. This involves a zero calorie branched-chain amino acids (BCAAs) beverage.
My fasting period each day begins the night before around 8 pm and continues into the next morning until 4 pm, for a total of around 20 hours. I am typically training during the mid-morning hours, thus I am in the middle of my final fasting hours before my evening feasting period begins.
In the initial waking hours after the previous evening's feast, my glycogen stores are still high enough to fuel a pretty heavy training and a moderately low intensity steady state or short high intensity cardio session. I sip the BCAAs before, during, and post training to reduce and recover any exercise-induced muscle damage. This helps maintain muscle mass and a provide a healthy basal metabolism rate while continuing to lose fat.
#2 - Use intermittent fasting it fits your health goalsEvidence supporting the health-related benefits of Ramadan fasting practices have been surfacing over the past few decades. These studies have demonstrated improved inulin sensitivity, glycemic control, and lipid profiles, all indicators for decreasing the risk of developing chronic lifestyle diseases such as diabetes.
In a twenty week study that combined intermittent fasting and calorie reduction in sixty obese women, it was demonstrated that this lifestyle was effective with weight reduction, visceral fat reduction, and lowered risk of development of coronary heart disease. The subjects also experienced a 9% body weight decrease from baseline.
In a controlled study that evaluated participants over a two year period, it was found that implementing a reduced calorie, nutrientdense intermittent fasting diet in a controlled ecological space yielded significant weight loss, decreased blood pressure and cholesterol levels, along with a lower fasting blood sugar and white blood cell counts.
Studies of these intermittent fasting practices on a longterm basis in various settings are still under review. 
#3 - Use intermittent fasting if it fits your lifestyleIf you need an effective weight loss strategy, ask yourself how consistently following a routine meal feeding and fasting frequency schedule will affect you mentally. If practiced, how long could you implement such practices? These questions were addressed in a literature review that looked at short to longterm fasting as treatment for obesity.
The study model looked at the short-term effects of a one-time, short-term fast of thirty-six hours. This is drastically different from the traditional daily Ramadan fasting schedule. However, when implementing a fasting regimen in otherwise healthy, lean male and female adults, the following conclusions were made:
- Short-term fasting of any type is effective for weight loss. The subjects in the study lost 1-2% body weight, which the researchers attributed to mobilization of glycogen stores and water versus metabolism of fat. Keeping in mind this study did not account for physical activity (i.e. strength training), of any type in the participants.
- The impact on psychological health was also addressed, as increased feelings of hunger were reported among the participants until a feed with a high-fat meal occurred.
- Long term implications support the introduction of practices such as intermittent fasting in the control of body weight and the potential for compensation both physically and mentally in otherwise healthy lean adults. Further study is needed to determine if these same outcomes will result in obese adults. 
Intermittent fasting is not a lifestyle choice that is a good fit for everyone, nor is it intended to be a form of starvation diet.
Conclusions and ConsiderationsScientists conclude that while current data supports short-term intermittent fasting as being beneficial to overall health, limited evidence is available to support effectiveness of long term use on general health in humans. The majority of research data available primarily involves animal studies. There is also a limited amount of data available with definitive implications for women and the potential impact intermittent fasting has on reproductive health. 
The overall take-home advice here is to evaluate your goals, your current health status, and overall lifestyle habits. Be sensible in incorporating fasting in to your lifestyle and listen to your body, keep a level head, and do your due diligence in evaluating the peer-reviewed scientific research journals.
Be leery of broad assumptions and trendy connotation in regards to fasting protocols as books written for the consumer market are designed to appeal to the positives, while overshadowing the negative in order to simply sell a book or idea.