Here are some of the PROS of IF:
- Decreases body weight--this is partly due to caloric restriction
- Decreases bodyfat--this occurs as a result of fatty acid oxidation
- Increases insulin sensitivity--this is due to lower blood sugar levels which causes the pancreas to reduce its insulin release
- Improves appetite control--this occurs as a result of PPY and ghrelin fluctuations
- Increases human growth hormone (HGH) levels--increased HGH is released from the pituitary gland to allow the body to use more fat for energy
- Increases metabolic rate (initial effect)--this occurs as a result of increased epinephrine and norepinephrine release
- Decreases risk of diseases--this is partly due to hormone changes lessening the onset of diseases like cancer and heart disease
- Improves cholesterol levels--LDL and HDL levels tend to decrease and increase, respectively and triglycerides tend to decrease
- Decreases blood pressure--this is due to a decrease in resting metabolic rate
Here are some of the CONS of IF:
- Catabolism--this occurs when muscle, which is a much more metabolically active tissue than fat, is broken down for needed energy when caloric intake has been reduced.
- Hypoglycemia--this involves low blood sugar levels which causes symptoms of hunger, headaches, weakness, and irritable feelings
- Bulging full feeling--caused by eating a relatively large amount of food within a short period of time
- Lethargy--this is caused by a lack of energy (read: calories) needed to fuel mental and physical activities
- Reduces metabolic rate (extended effect)--this is partly due to elevated cortisol, a stress hormone
BOTTOM LINE: IF may work for some people who are disciplined at dieting and are able to withstand hunger pangs. Keep in mind that most of the research on IF has been done on animals. The effects of IF on animals may not be applicable to humans. IF is NOT recommended for diabetics due to the fluctuations in blood sugar levels. IF is also NOT recommended for bodybuilders who aim to preserve muscle mass when dieting. The outcomes of regular meal feedings include:
- increased metabolic rate
- balanced blood sugar level
- muscle mass maintenance
- decreased bodyfat
MY RECOMMENDATION: Listen to the hormonal signals provided by your body which indicate hunger and eat. There are easier ways to lose body weight without causing dramatic fluctuations in blood sugar levels. Gradually reduce your caloric consumption while stepping up your physical activity. Eating healthy (i.e., less processed foods) and exercising regularly will lessen disease risk, improve cholesterol levels, and reduce hypertension without resorting to a trendy diet like intermittent fasting that most likely will not be sustainable.
If you still want to try IF, it is recommended to fast for no longer than 20 hours to lessen muscle catabolism and nutrient deprivation. Also, you may want to start conservatively by fasting only one day per week for several months to see how your body responds. Depending on how you look and feel, then make a decision on whether to add another fasting day per week or try something else. Remember, always listen to your body--it never lies!
Brian Danley, CFT
"Motivation is what gets you started. Habit is what keeps you going."