QUOTE from Dr Fung (emphasis mine):
CONVENTIONALLY, DIET AND exercise have been prescribed as treatments for obesity as if they are equally important. But diet and exercise are not fifty-fifty partners like macaroni and cheese. Diet is Batman and exercise is Robin. Diet does 95 percent of the work and deserves all the attention; so, logically, it would be sensible to focus on diet. Exercise is still healthy and important—just not equally important. It has many benefits, but weight loss is not among them. Exercise is like brushing your teeth. It is good for you and should be done every day. Just don’t expect to lose weight. 
Can I exercise while fasting?
ABSOLUTELY. THERE IS no reason to stop your exercise routine. All types of exercise, including resistance (weights) and cardio, are encouraged. There is a common misperception that eating is necessary to supply “energy” to the working body. That’s not true. The liver supplies energy via gluconeogenesis. During longer fasting periods, the muscles are able to use fatty acids directly for energy. As your adrenalin levels will be higher, fasting is an ideal time to exercise. The rise in growth hormone that comes with fasting may also promote muscle growth. These advantages have led many, especially those within the bodybuilding community, to take a greater interest in deliberately exercising in the fasted state. 
NOTE (my commentary)
Most “experts” want to have us lose weight by working it off by exercise. This is part of the same pattern of denial, which is to ignore the importance of diet and focus our attention elsewhere. It is a natural pattern of denial, to give lip service to diet and then focus energy and attention on actually reaching our goals through exercise. But, as Dr. Fung points out, “Diet does 95 percent of the work and deserves all the attention; so, logically, it would be sensible to focus on diet.”
Rather than work out to burn fat, we can simply live (and fast) as a means of encouraging the body to switch to burning fat. Which takes more effort and therefore engenders more resistance? To me, it would be my exhausted and sweaty body trying to burn one pound of fat by exercise. How much exercise is needed, if we attempt to lose weight by adding exercise to our day? A pound is the equivalent of 3500 calories.
We burn a pound when we ride an exercise bicycle at a moderate pace for … 7 hours. Full tilt, all out, perhaps in 2.5 hours of non-stop sprinting. A methodical 5 mph (12-minute mile pace) of running will burn a pound in … a little less than six hours without breaks.
But – normal living burns an estimated 11 calories per pound per day. A person weighing 318 pounds … a little bit less than my weight for the past year … burns 3500 in a day just breathing and through normal activity. So, compare the two choices – #1, eat normally but run for six hours straight without a break. Choice #2, do not eat (fast) and live your normal day and burn 11 calories per pound that you weigh by not doing any exercise. My choice will always be choice #2.
But, someone will say, exercise boosts our metabolism! True, but fasting also boosts your metabolism while you are fasting. Our bodies are created to hunt and seek food when we have had nothing to eat, and energy is needed for that activity.
“Can I exercise while fasting? Absolutely, there is no reason to stop your exercise routine,” says Dr. Fung. But the most effective exercise for weight loss is to simply not eat. Your body will get energy from burning fat. In fact, exercising while fasting has many advantages.
If diet does 95 percent of the work, I will intentionally focus on diet rather than exercise as my strategy for losing weight and burning my own body fat.
What gets my attention?
Do I understand the need or problem?
Do I understand the potential solution?
Do I understand how to apply that strategy?
What questions do I have for the experts? What might be the answers?
Who needs to hear this?
What do I do next?
 Quote from The Obesity Code: Unlocking the Secrets of Weight Loss by Dr. Jason Fung; Greystone Books (March 3, 2016). Page 53-54.
 Quote from The Obesity Code: Unlocking the Secrets of Weight Loss by Dr. Jason Fung; Greystone Books (March 3, 2016). Page 252.
 “Burn 500 Calories In An Hour” from https://www.realbuzz.com/articles-interests/fitness/article/burn-500-calories-in-an-hour/
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Key: Fung-06 Shipped: 05/04/2021. Updated 01/11/2022.