I’d already heard about muscle loss problems before I started the diet so I just keep to the same mix on fast days….just alot less. So, some protein, some carb, some fat. All are essential..just not in the quantities I was taking in before! An egg, a 100g chicken breast, a few slices of parma ham….all sources of protein, around 100 cals each.

I’ve lost 5kg using the 5:2 diet and my Fat free mass has stayed constant at 64kg throughout the process indicating that it appears to be only fat that I am losing. I eat a big bowl of porridge in the morning on fasting days and haven’t made an effort to eat more protein but it doesn’t seem to have made a difference. I think I read somewher that Growth Hormone levels are elevated during the first 24 hours of fasting and this has a protein sparing effect.

I’ve noticed my muscle tone actually improve, rather than decrease since starting the diet. Though I suspect this is less fat covering them rather than increased muscle size. Given that the fasting is for a fixed period of time there’s no reason why it should eat into your muscle mass – this is more of a problem on low calorie diets which you sustain over several weeks or months – where your body goes into starvation mode and burns muscle which has a detrimental effect on your metabolism and is one of the reasons such diets don’t work in the long term. With IF your eating again before your body needs to start using up muscle, so you should burn mainly fat rather than muscle.

I’ve been on a 5:2 regime for a couple of weeks now and happy with the progress thus far and still researching this topic as I go along. I have come across some research published on pub med as follows and wonder if Michael or others have any comments please:

http://www.ncbi.nlm.nih.gov/pubmed/21816219

Abstract
Calorie restriction is a dietary intervention known to improve redox state, glucose tolerance, and animal life span. Other interventions have been adopted as study models for caloric restriction, including nonsupplemented food restriction and intermittent, every-other-day feedings. We compared the short- and long-term effects of these interventions to ad libitum protocols and found that, although all restricted diets decrease body weight, intermittent feeding did not decrease intra-abdominal adiposity. Short-term calorie restriction and intermittent feeding presented similar results relative to glucose tolerance. Surprisingly, long-term intermittent feeding promoted glucose intolerance, without a loss in insulin receptor phosphorylation. Intermittent feeding substantially increased insulin receptor nitration in both intra-abdominal adipose tissue and muscle, a modification associated with receptor inactivation. All restricted diets enhanced nitric oxide synthase levels in the insulin-responsive adipose tissue and skeletal muscle. However, whereas calorie restriction improved tissue redox state, food restriction and intermittent feedings did not. In fact, long-term intermittent feeding resulted in largely enhanced tissue release of oxidants. Overall, our results show that restricted diets are significantly different in their effects on glucose tolerance and redox state when adopted long-term. Furthermore, we show that intermittent feeding can lead to oxidative insulin receptor inactivation and glucose intolerance.

I’m a student doing a co-op program at a gym, and I was given an assignment to research the IF diet but I can’t seem to find some of the answers I’m looking for. If you workout daily then how are you suppose to have energy for the workout on the fast days? And do you just have your second meal as your post-workout?

I have found that eating one meal daily at 5 pm works best for me with a 23 hour fast M-F, and then 1-2 meals on weekends…I feel fantastic and have so much more energy…..I am thinking (hoping) that this will bring the same results with my IGF levels…I eat normal for my one meal daily, and also take vitamins and a dehydrated veggie/fruit pack every 24 hours with my meal. Cannot tell you how many benefits…sleeping better, improved focus, happier….better quality of life after just two weeks!.

Is there any evidence about the impacts of fasting on the gall bladder? particularly intermittent fasting?

I’ve been on the 5:2 for coming up to a year now (lost about 15lb in the first 6 weeks and about 2-3 since). I’m a keen cyclist and train fairly hard. I have slowly been developing the training I can do on fasting days, starting with 3/4 effort (zone 4/HR) and gradually increasing it to around 90-100%. As long as I keep the ride under 100 mins I don’t feel any side affects, apart from the odd cramp from not having my normal hydration drink (just water). My question is this:

I regularly get Personal records on Strava segments on fasting day. Any idea why? Is it because I’m a tiny bit lighter on fasting day or is there some other reason why I can push harder for a short segment. I would expect my body to be running on empty?

I lift weights and do cardio several times per week. I started the 5:2 diet 8 months ago and continued the same exercises. In addition I follow a low animal protein diet. I was concerned from the start that I would get weaker, and initially I did lose a little strength as measured by the heaviest weights and repetitions. However, surprising to me is that now even on a strict 5:2 (36 hours with < 600 calories) and low protein I am lifting as much as I ever had before and some weights are higher now than ever. I was thin to start and am now even thinner but muscle definition is very good. I am not doing any of this for appearance but for health. I believe it is important to stay lean, minimize animal protein, and exercise. I feel very comfortable that I am not losing any muscle mass and somehow am getting stronger. Negative side effects besides hunger are tiredness on fasting days, and occasional diarrhea the next day.

I believe intermittent fasting helps in building strong and lean muscles. That is what i have experienced during my training.

Information source for intermittent fasting: http://www.jmaxfitness.com/

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So…

“David Lau, an obesity researcher, professor and chair of the diabetes and endocrine research group at the University of Calgary. When glycogen stores in the liver are depleted, the body doesn’t burn fat: It breaks down protein. Lau said starvation will only burn fat as fuel after about a week of starvation.

“Muscle protein breakdown occurs in the first 24 hours of starvation,” he said. “Muscle protein breakdown [is] not healthy.”

His concern is that many people are fasting without realizing they may be losing crucial muscle mass. The danger is that as protein in the body breaks down, it could lead to other unwanted side effects, such as altered immunity. In order to fight infections, the body needs to produce antibodies, a type of protein. But when the body is breaking down protein for fuel, it may not send the right signal to make antibodies, Lau said.”

But… as Dr Jason fung put is in many a video and in this article: https://intensivedietarymanagement.com/fasting-and-muscle-mass-fasting-part-14/

“Muscle gain/ loss is mostly a function of EXERCISE. You can’t eat your way to more muscle. Supplement companies, of course, try to convince you otherwise. Eat creatine (or protein shakes, or eye of newt) and you will build muscle. That’s stupid. There’s one good way to build muscle – exercise. So if you are worried about muscle loss – exercise. It ain’t rocket science. Just don’t confuse the two issues of diet and exercise. Don’t worry about what your diet (or lack of diet – fasting) is doing to your muscle. Exercise builds muscle. OK? Clear?Macro oxidation

So the main question is this – if you fast for long enough, doesn’t your body start to burn muscle in excess of what it was doing previously in order to produce glucose for the body. Hell, no.

Let’s look carefully at this graph by Dr. Kevin Hall from the NIH in the book “Comparative Physiology of Fasting, Starvation, and Food Limitation”. Great title guys. Amazon probably couldn’t keep enough stock on the shelves.

But anywho, this is a graph of where the energy to power our bodies comes from, from the start of fasting. At time zero, you can see that there is a mix of energy coming from carbs, fat and protein. Within the first day or so of fasting, you can see that the body initially starts by burning carbs (sugar) for energy. However, the body has limited ability to store sugar. So, after the first day, fat burning starts.”

In my experience, I’ve been IF for five consecutive days midweek throughout Feb and into March. I do gym work, swimming, running and cycling. My lean muscle mass went up in Feb. My running is quicker than when I started 5:2 last Sept. mainly due to the weight loss I think – carrying around 10kg more than I am now when running seems quite extraordinary!

So from this sample of one I can conclude the Professor is a charlatan (allegedly) or at best mis-guided. I’ve not read the study on the mice, but Dr Fung makes it clear that the natural process of muscle loss and replacement accounts for some of the urine contents, and all that skin that seems to miraculously disappear as we lose weight, (rather than us look like an empty sack of skin) also gets eaten-up.

And finally, I don’t think I’ve come across anyone on this forum who moans about muscle lost, rather than fat loss!! As the ardent faster Dr Fung says himself, he would have disappeared by now if a large proportion of what he’d lost was protein and not fat. So for heaven’s sake can these Professors think before they pontificate. Let’s remember there are a bunch of very eminent Profs out there who got us all eating high carb-based diets. Even the NHS Healthy Balanced Diet has high carbs, and the evidence in the UK and elsewhere that this is just plain wrong is huge! One big experiment that has led to a rapid growth in Type 2. Or a: “Diabetes Tsunami” – to quote Prof Lau.