The types and quality of food you eat influences more than how much you weigh. Food has an effect on your metabolism, insulin production, leptin release and a myriad of other hormonal and chemical balances.
Scientists are also examining the way fasting affects cellular and mitochondrial function, and longevity.
They've found the cells in your body react to fasting in much the same way as they do to exercise. In other words, when placed under stress — be it exercise or fasting--the reaction creates changes at the cellular level that helps extend your lifespan. 
For starters, fasting shifts your body from using glucose as its primary fuel to fat, and being an efficient fat-burner benefits your health beyond weight loss.
Although much of the research is on fasting or intermittent fasting, the newer term is sometimes referred to as TRF (Time Restricted Feeding) which promotes eating in a narrow window of time, typically 6-8 hours.
Efficient Fat Burning Promotes Health
Fat is a far cleaner burning fuel than carbohydrates and generates far less free radicals,
Glucose is an inherently "dirty" fuel as it generates far more reactive oxygen species (ROS) than fat. But to burn fat, your cells must be healthy and normal. Cancer cells, for example, cannot burn fat, and this why a healthy high fat diet appears to be such an effective anti-cancer strategy.
We're now starting to realize that mitochondrial dysfunction is at the core of virtually all diseases, and nutritional intervention — not only what you eat, but also when, and how often — is of key importance.
To summarize, mitochondrial health is promoted by eating real food; avoiding food at least 3 hours before bedtime; and intermittently fasting.
What Happens When You Fast?
Fasting is a biological stressor with several amazing health benefits, including normalizing your insulin and leptin sensitivity, promoting human growth hormone (HGH) production, reducing oxidative stress and lowering triglyceride levels.
And now a team of researchers from the University of Southern California believe they have discovered yet another benefit: The regeneration of stem cells. 
During the initial 14-16 hours of not eating, your body burns through almost all of your carb (glycogen) stores in your muscles and liver. Once those glycogen stores have been depleted, your body turns to fat stores for energy. Intermittent fasting teaches your body to efficiently burn fat for fuel.
Intermittent Fasting Can Help Regenerate Your Entire Immune System
In an adult, the undifferentiated stem cells found in tissues and organs are used by the body to renew itself. The primary role of these cells is to maintain and repair the tissues where they are found. 
Another effect of fasting is autophagy. When this vital process occurs in the mitochondria it is called mitophagy. This is when your body begins to eat itself in an orderly pattern to remove damage parts from your body.
Although it sounds like something you'd want to avoid, this particular process is healthy and helps your body to "clean house." According to Colin Champ, M.D. and certified radiation oncologist at the University of Pittsburgh Medical Center: 
"Think of it as our body's innate recycling program. Autophagy makes us more efficient machines to get rid of faulty parts, stop cancerous growths, and stop metabolic dysfunction like obesity and diabetes."Mitophagy happens at the cellular level where the membranes break down and your body recycles what's healthy and uses the rest for energy, or to make new parts. This process may also play a role in controlling the amount of inflammation in your body.
When scientists engineered rats incapable of autophagy they grew up sleepier, fatter, with higher cholesterol levels and impaired brains. [5,6]
Three Strategies That Promote Mitophagy and Cellular Regeneration
There are three ways to elevate your body's ability to destroy worn out cells and regenerate new ones. The first is exercise, which puts stress on your body, tears down muscle, and helps your body to rebuild new tissue.
A highly effective way to boost mitophagy is intermittent fasting. Some studies even suggest intermittent fasting can improve cognitive function, brain structure, and help you to learn more easily.  These studies were completed on rats and it wasn't totally clear if the benefits resulted specifically from autophagy.
Yet another way to mimic mitophagy is to use a high fat diet consisting mainly of high quality healthy fats with a moderate amount of high quality protein and minimal non- fiber carbohydrates in the ratio represented in the graph below The idea is to reduce your carbohydrate intake to a level that your body has no other choice but to burn fat for fuel.
Research demonstrates this diet will help your body fight cancer, lower your risk of diabetes, fight some brain disorders, and can reduce seizure activity in 50 percent of children on the diet by at least 50 percent. [8,9]
Keep in mind that monitoring your protein intake is just as important as cutting non-vegetable carbs. If you eat more protein than what your body needs, you will prevent the activation of pathways associated with stem cell and immune system regeneration. This includes the mTOR, PKA, and IGF pathways. 
Timing Your Meals Right Can Cut Free Radical Damage
There is compelling evidence that when cells are supplied with fuel when fuel is not needed, the cells leak electrons that react with oxygen, producing free radicals. Free radicals are responsible for damage to your cells, DNA, and have been linked with an increased potential for illness and disease.
The best way to reduce free radical damage is not to take antioxidants but to make sure you are burning a clean fuel like fat and not carbs. However, when your caloric intake is greater than necessary, and especially when consumed at a time when you have low energy needs, like when you are sleeping, it increases the number of free radicals produced. 
Studies have demonstrated the link between free radicals and mitochondrial DNA damage, which is then responsible for producing nuclear damage that can result in cancer. In a study from France, researchers demonstrated in a mice model that intermittent fasting in mice with lymphoma reduced the amount of free radical, increased their longevity and reduced the death rate. 
This is also why I recommend not eating at least 3 hours before bedtime. Your body will use the least amount of calories when sleeping, so the last thing you need is excess fuel at this time, as it will generate excessive free radicals that can damage tissues, accelerate aging, and contribute to chronic disease.
Personally I stop eating around 4 – 5 PM, but this time varies depending on what my blood sugars are running. My goal is to have a fasting blood sugar below 60, but certainly below 70.
I personally strongly disagree with fasts much longer than 18 hours as it will drive most people into burning lean muscle mass for fuel. This is why I recommend 16-18 hours of fasting each day and eating all of your calories in the remaining six to eight hours. This reduces your body's dependence on carbohydrates and glycogen on a daily basis. Research has demonstrated a lowered cancer risk and improved weight management in both humans and animals. 
How to Support Intermittent Fasting
Intermittent fasting is healthy for most people. However, if you suffer from diabetes, hypoglycemia, chronic adrenal stress, or cortisol dysregulation, you must take specific precautions and work with your physician and dietitian to ensure healthy balance of nutrition and fasting. Pregnant and nursing mothers should not fast as their babies need the nutrition to grow and develop appropriately.
Adding this type of fasting to your health regimen may be challenging but the rewards are significant. Begin by using a fasting schedule you think you can maintain. Don't get discouraged if you eat more on your fasting days than you had planned. Drink plenty of water and tea to help feel full and satisfied during the day.
Get support from friends or relatives. Starting a program with someone else, especially in the same house, will give you an accountability partner with whom you can share tips that work for you. When you know that someone else is counting on you to walk this journey with them, you're less likely to eat more than you planned.
To sum it all up, intermittent fasting improves your immune system and mitochondrial function, reduces your inflammatory process and the amount of free radicals in your body. It is also dramatically helps to slow down the aging process, especially if you eat your macronutrients in the ratios in the chart above. In other words, going without food now and then is not going to kill you — on the contrary, it may be one of the keys to living a longer and healthier life.
Sources and References
1, 10 CNN. March 9, 2016
2 Fasting triggers stem cell regeneration of damaged, old immune system. (2014). News.usc.edu. Retrieved 15 March 2016
3 What are adult stem cells? [Stem Cell Information]. (2016). Stemcells.nih.gov. Retrieved 15 March 2016
4 Greatist February 29, 2016
5 Rosenfeldt, M., & Ryan, K. (2011). The multiple roles of autophagy in cancer. Carcinogenesis, 32(7), 955-963
6 Greatist February 29, 2016
7 Stipp, D. (2012). Is Fasting Good for You?. Sci Am, 308(1), 23-24.
8 Journal Of Cancer, 135(7), 1711-1720.
9 Ketogenic Diet. (2016). Epilepsy Foundation. Retrieved 15 March 2016
11 The Benefits Of Intermittent Fasting & Exercise | Live Trading News. (2016). Live Trading News.
12 Mechanisms Of Ageing And Development, 126(11), 1185-1191. Retrieved
13 Meal frequency and timing in health and disease. - PubMed - NCBI. Ncbi.nlm.nih.gov