Basic information about the diet
The Fasting Mimicking Diet (or Fasting Mimetic Diet; either way, FMD for short) is a five-day “fast” that was developed by Dr. Valter Longo of the University of Southern California. The quotation marks are used because you don’t actually forgo food entirely, but are allowed to eat about 1100 calories the first day and then around 750 cals for the remaining four days. Longo has patented his diet and founded a company called Prolon that sells boxes containing five days’ worth of food for those thinking about trying the FMD.
Longo maintains (and has a lot of data to support the idea) that doing a five-day FMD confers several significant health benefits. Primary among them are a loss of abdominal fat (and specifically VAT, or Visceral Adipose Tissue, i.e., the fat around the organs that’s especially hard to get rid of), anti-aging benefits and a resetting of certain components of the immune system. The FMD apparently will benefit cancer patients and those with auto-immune diseases such as Multiple Sclerosis, Gillain-Barré Syndrome, CIDP, etc.
I ordered a few boxes and tried the diet out for myself. Here’s what I learned.
My experience with the FMD
The food tasted pretty good, considering. You have a nut bar for breakfast (which tasted about the same as any other granola bar), and some kind of soup for lunch and dinner. There are kale crackers or a small (Like, SMALL dude. Like two inches square.) chocolate bar for a few extra calories. And there is a drink mix that you sip throughout the day on days 2-5. Other than that, it’s a package or two of olives and some vitamins.
I experienced very little hunger. It’s really surprising, given how few calories you take in during the diet, but proper food choices really do seem to blunt hunger pangs. I became more of a fan of soups and teas during the five days, and will incorporate more of them into my regular diet going forward.
That said, it wasn’t like I felt full or anything. I did the diet from Monday through Friday, and if you work a regular job I suggest that you do the same thing. One woman who tried the diet did it over a weekend and found herself constantly focusing on her stomach because, without work or any social engagements, there was nothing to distract her. And I agree: it’s a good idea to have some work or project or something that you plan to get done during the time you’re dieting. If you can’t come up with anything, now would be the time to binge-watch that Netflix series you’ve been putting off, or else get really caught up in an online game for a few days. Whatever you choose, make sure you have something to take your mind off food.
Hunger did increase if I exercised. I did some light kettlebell work on Monday, went to the gym for a light weight workout on Wednesday. On Thursday I went for a half-hour walk. The walk didn’t have much effect, but I definitely felt hungrier on the days I did any kind of weight work.
On the other hand, I never felt lightheaded or weak. This is probably a very individual response, so if you decide to exercise, do so with caution. The only reason I did it was because (a) I was going stir-crazy just sitting around the house and (b) I wanted to try to maintain as much lean body mass as possible. I’m an ectomorph, which means that my LBM tends to vanish if I don’t take steps to keep it. I don’t have a problem with weight gain, it’s weight loss that’s the issue.
Another thing was, I developed a healthy respect for the ability of tea to cut hunger. It’s one of the cornerstones of the Prolon program; it gives you four bags of tea for each day, and you drink them with each meal and for an afternoon “snack”. Each time I did, I was good for a couple of hours after. You can also have one – but only one – cup of unsweetened coffee if you’re a coffee addict. Since I’m not, I didn’t.
Results: I went into the diet weighing a little over 81kgs and having a bodyfat of 19.6% as measured by InBody 370. After a couple of days I had dropped about a kilo, most of which was probably water weight.
The great benefit of ordering a Prolon diet kit is that all (and I do mean ALL) of the guesswork is taken out of the fast. You know exactly what to eat, when to eat it, and how far you can go with “cheating” (not very far). It’s been specifically formulated to provide you with all the nutrient-dense calories you need during the fast.
The big drawback is the price. Even at the bulk discount rate, one box will set you back US$225, which seems a bit much for a week’s worth of powders and crackers. Furthermore, if you live in a country where Prolon doesn’t ship, you’ll need to pay quite a bit more just to get the box delivered. (In case you think that Valter Longo is getting rich off this, his portion of the proceeds are donated to research.)
I bought three kits and will be using those for my first three FMDs. But because of the price, after that I’ll be experimenting with eating my own foods, just following the macronutrient figures and rules Longo gives in his patent. These are:
Day 1: Total caloric intake of 4.5 to 7 kcal/lb of body weight (10% protein, 56% fat, 34% carbs)
Days 2-5: Total caloric intake of 3 to 5 kcal/lb of body weight (9% protein, 44% fat, 47% carbs)
Both protein and sugars are separately limited to less than 15% of the total cals for the day.
So if you weigh 180lbs (about 82kgs), you would aim for 1080 calories the first day and 720 cals the rest of the days. Of these, only a maximum of 160 would be protein and 160 would be sugar the first day; those numbers go down to 108 for days two through five. Longo recommends that all of the protein come from plant-based sources for best results. I would add that you don’t want any starchy carbohydrates in there either.
So how did the FMD work for me?
I used an InBody 370 machine to track my weight, fat and muscle before and after the diet. Here are the numbers:
Before the diet (28 Oct):
Weight: 81.3 kgs
Bodyfat: 19.6%
Fat: 15.9kgs
Muscle: 36.6kgs
Last day of diet (2 Nov):
Weight: 79.0kgs
Bodyfat: 19.0%
Fat: 15.0kgs
Muscle: 36.0kgs
As you can see, the FMD is not magic. Like any other diet, it will not strip away just the fat and leave your muscle completely intact during the fast. But it does work better than water-only fasting, that’s for sure. I lost about 2.3kgs of bodyweight, of which 0.9kgs was fat and 0.6kgs was muscle. So that’s a 1.5:1 ratio, keeping the muscle and losing the fat, which, if not ideal, isn’t too bad.
However…then comes the refeed, when you go back to your regular eating habits. I had two meals the day after the diet ended before I went back into the gym for a “real” workout, and those two meals were a large pancake for breakfast and a dish of cheesy gratin (about 500cals) for lunch. Also had a few raspberries and grapes along the way. So pretty much all carbs, mostly starch, with a little protein (meat sauce and cheese on the gratin). The results were not great:
One day (two meals) after diet (3 Nov):
Weight: 78.4kgs
Bodyfat: 19.0%
Fat: 14.9kgs
Muscle: 35.7kgs
An additional 0.3kgs of muscle lost vs only 0.1 kg of fat. So the next time I do the diet (link will be posted at the bottom of the page), I will eat more in the way of calorie-dense vegetables and/or protein. Try and gain some weight back without triggering fat accumulation.
Four days after diet (6 Nov):
Weight: 79.6kgs
Bodyfat: 18.3%
Fat: 14.6kgs
Muscle: 36.6kgs
Now that’s more like it. Muscle has returned (exactly) to pre-FMD levels, while the fat is 1.3kgs less. So almost all of the weight difference is due to fatloss, with a little wiggle room for tester inaccuracy and some water fluctuation.
So four days out from the diet, the FMD has to be judged an unqualified success. However, I wanted to see how far the refeed/compensation (and maybe even some super-compensation) would extend.
Six days after the diet (8 Nov):
Weight: 79.0kgs
Bodyfat: 17.3%
Fat: 13.7kgs
Muscle: 36.9kgs
More fatloss, along with a slight gain in muscle. It was kind of unbelievable that these results could come from a fast. But it was true according to the InBody machine, and also true that I was just as strong (if not stronger) in the gym as I was before the diet even though I was about two kilos lighter. So I guess the muscle was preserved.
Interestingly enough, on pull-ups, which is a bodyweight exercise and therefore one movement that you would think would be easier at a lighter weight, I was only “as strong”. When using barbells or machines, though, I was stronger on virtually every exercise. For example, in my last workout before the FMD, I used 130kgs on legpress and got three sets of six reps. First workout after the FMD, I got 7, 7 and 6 reps on the same exercise using the same weight.
Twelve days after the diet (14 Nov):
Weight: 79.6kgs
Bodyfat: 16.3%
Fat: 13.0kgs
Muscle: 37.6kgs
Tips for getting the most out of your fast
Make liberal use of the teas. I’m not normally a tea drinker, but the caffeine in the teas that are provided really do go a long way toward staving off or eliminating hunger. I drank all of my tea almost every day, especially the first couple of days of the fast.
Pro tip: Mix the lunchtime soup powders into warm water. Even though you’re going to microwave the soups, if you mix them with cold water, the soup powder will clump and become very sticky. This will still happen a little with warm water, but it’s not nearly as bad.
One final piece of advice
As I was surfing around the Net to see how other people had done on the FMD, I was surprised to find that a number of them had experienced nausea and/or failed to complete the diet. I had no such reaction. But then I’ve done ketogenic diets before, and it’s true that the first time tried one, I felt fuzzy and “out of it” for two or three days until my body made the adjustment. (In subsequent keto dieting, I never had the problem again.)
So if you’ve never done a ketogenic diet, never been in ketosis, then I strongly urge you to try just that once or twice, at isocaloric levels (meaning that you eat the same amount of calories as your normally would, just get them from keto sources instead of carbohydrates), before you attempt the FMD. The FMD puts you into ketosis AND drastically lowers your overall calories, and apparently for some people that’s just too much to handle at once.
So break it up. Get used to burning ketones for fuel, and then once you’ve made that switch go ahead and try the FMD. There should be no reason for you not to succeed.
UPDATE: Here is a link to the second time I tried the FMD.