Improving Body Composition
What we've been doing and why
In order to reduce visceral fat while maintaining muscle and bone, Gretchen and I have developed our own version of a 'fasting mimicking diet,' a five-day meal plan that achieves the benefits of water-only fasting without the downsides. So far so good!Introduction
I shudder whenever I hear talk of “losing weight”. It can be the most health-damaging effort anyone can undertake.
The biggest problem with losing weight: often a lot of the tissue lost is muscle1 and even bone. But nearly everyone needs MORE muscle. Muscle is valuable for preventing falls and the resulting fractures2 — especially as you get older — but it’s not just about strength. Muscle and bone are your primary biomolecule reservoirs supporting immune function, hormone production, healthy bone reconstruction and numerous other essential processes.
In recent years, I’ve even been searching for ways to retain subcutaneous fat (which helps regulates body temperature and cushions deep tissues from blunt trauma3) while somehow targeting visceral fat (stored around and within abdominal organs) which increases risks of heart disease, stroke, diabetes, high blood pressure, cancer, fatty liver disease, dementia … the list of demonstrated risks keeps growing.
=> Disclaimer
Table of Contents:4
The First Step
So in order to improve body composition rather than lose valuable tissues in addition to fat, it’s crucial to start the process by focusing on fitness — rather than weight — as Chris Masterjohn, Nutritional Sciences PhD, advises in the first rule from his recent article on ‘How to Lose Fat Without Losing Muscle’:5
[When you begin] Exercise more, do not eat less. […] get your total resistance training and high-intensity workouts up to six hours per week with the base of this being full-body resistance training and the remainder high-intensity intervals and sprints. Add some moderate intensity work on top of this base and lots of light activity like walking. [… Only after achieving this level of fitness is it] time to cut food intake.
While Gretchen and I do have occasional weeks with six or more hours of high-intensity exercise, at our age — mid-60s — we only shoot for two hours a week. To this we strive to add a few hours weekly of ‘Zone 2 training’ and at least an hour daily of walking. We’ve maintained this for most of our lives, so we feel ready for occasional periods of caloric reduction.
Fasting Mimicking Diet (FMD)
Late last year, I heard an interview with Joseph Antoun, MD, PhD on the Wise Athletes podcast. Dr. Antoun, CEO of L-Nutra, claimed that his company’s Prolon Fasting Mimicking Diet targets visceral fat without sacrificing muscle mass.
I first learned about Prolon/FMD about five years ago in an interview with L-Nutra’s founder, Valter Longo, PhD. Dr. Longo’s focus in that interview was on preventing and even treating cancer.6
Soon thereafter, one of my doctors began selling Prolon in his practice to help patients reduce inflammation. I remember thinking it was way too expensive for five days of low calorie meals. The figure $500 comes to mind, but either my memory is wrong — definitely possible! — or the price has come down quite a bit.7
In the Wise Athletes interview, Dr. Antoun explained that the first twelve hours of fasting is totally beneficial; but even though longer fasting periods produce additional types of benefits, they only do so at the expense of increasing costs.8 FMD captures the benefits — in particular, increased autophagy that typically begins after 72 hours of fasting — while maintaining muscle by providing sufficient protein intake so that the body primarily metabolizes fat for fuel, rather than indiscriminately tapping from all fuel sources.9
The Prolon 5-day FMD program provides a meal plan that mimics the effects of fasting to promote cellular rejuvenation and fat burning and protect muscle mass. Each day's package includes a plant-based soup, nut bar, snacks such as olives and kale crackers, herbal tea and a glycerol-based drink, plus a supplement formula containing vitamins, branched-chain amino acids, minerals and omega-3 fatty acid.
Our Experience with iFMD
During the week before we traveled to a family gathering for Christmas, Gretchen and I first tried out our own version of FMD, which I’ll refer to as iFMD — “improved FMD” — since we made numerous improvements to L-Nutra’s Prolon product.
For iFMD, we eat two meals and two snacks each day that we prepare almost entirely from grass-fed animal food sources and a wide variety (about 50 species) of whole organic plants. For meals we eat things like bone-broth based vegetable soups, eggs, lamb and/or liver. For snacks we eat nuts and seeds (sprouted, when available), olives and kale, plus homemade unsweetened dark chocolate. Autophagy, the breakdown of damaged cell components, is one of the major goals of (mimicking) fasting so we avoid supplementing anti-oxidants that suppress it. During iFMD we keep up a full body exercise program so that our muscles and bone signal that they want to be maintained. To limit tissue damage, we back off the highest intensity. See the section below on “iFMD: Improvements to Prolon/FMD” for additional details.
The timing was great: iFMD offset the pigging out we did during our Christmas trip!
After the New Year, we repeated iFMD a second time, and completed a third week at the end of January.10 We’ve just completed a fourth iFMD.
Whereas we had found it difficult to water-only fast beyond 2.5 days — at that point having trouble with both falling and staying asleep — we were comfortable with iFMD for the full five days. In particular, we slept well and only felt hungry a little more often than usual.
We’ve both sensed a reduction in inflammation from iFMD. For example, recently I’ve had a bit of soreness in a knee ligament which disappears during iFMD.
Each episode produces a large weight loss, but — as with many other diets — that’s mostly due to shedding water which is gradually restored after resuming our usual diet:
Since we don’t plan to do any DEXA scans we will need to repeat the process a few more times to see if we are achieving significant visceral fat reduction while maintaining muscle mass.
One indication that we’re maintaining and possibly even gaining muscle is that both of us set a number of personal bests in long track speed skating time trials following each of our first three iFMD weeks.11
One possible sign that I’ve metabolized visceral fat via iFMD is that my heart rate monitor chest strap has started to slip down during exercise, perhaps due to reduced girth just below my sternum.
In terms of our home blood tests, iFMD does mimic fasting:
Blood glucose: 57 to 65 mg/dL.
Ketones (beta-hydroxybuterate): 1.7 to 3.1 mmol/L.
We’ve been pleasantly surprised that — after each return to our regular diet — we haven’t had an urge to snack after dinner. … I would have thought we might have the opposite response: that is, less appetite control after five days of restriction.
Concerns about FMD (and even iFMD)
iFMD should generate the benefits of multi-day fasting while reducing the downsides, but I doubt if it can eliminate them. We felt more cold sensitive during our fasts, indicating downregulated metabolism. Cold sensitivity ended with normal feeding, but it does seem prudent — as L-Nutra advises — to limit FMD to five days per month in order to avoid permanent downregulation.
Based on the research of Herman Pontzer and his colleagues that led to their ‘Constrained Energy Expenditure Model’ …
… fat metabolization appears to be limited to about 1% of total body fat daily.12 Attempting to further increase caloric deficit — whether through cutting more calories and/or increasing physical activity — won’t burn more fat, but instead reduces hormone production, immune response, warming of peripheral tissues, etc. So it’s important not to be too aggressive with (i)FMD.
iFMD: Improvements to Prolon/FMD
We’ve made numerous enhancements to L-Nutra’s Prolon product:
Individualized caloric intake: Rather than Prolon’s one-size-fits-all — 1100 calories on day one, followed by 700 to 800 calories on days two to five — we adjust calorie intake as a percentage reduction from our typical consumption. Prolon appears to be based on a 2000 calorie per day baseline. Since I usually eat 3000 to 3500 calories/day, I targeted 1600 calories on day one, followed by 1200 calories on days two to five.13 I suspect that, for me, reducing to 800 calories daily would require breaking down muscle in order to (inadequately) support homeostasis.
Protein: Digestion breaks down proteins into individual amino acids and very short chains of two or three amino acids that can be absorbed in the digestive tract.14 Our bodies use 20 different amino acids to construct proteins and facilitate other biosynthetic pathways. Many of these amino acids can be synthesized from others, but nine of them are essential amino acids — EAAs — because they can’t be synthesized. In addition, six more are conditionally essential amino acids because they can’t be sufficiently synthesized under certain conditions such as inadequate dietary precursors — likely to be the case during FMD — or stress. So general protein quantity recommendations can be off target because what really matters is your diet’s specific amino acid composition.
— Amino acids that aren’t utilized15 are metabolized via deamination, generating nitrogen-containing waste products such as ammonia and urea that are toxic in high concentrations. Eggs are the common food with the highest amino acid utilization, but even so, about half of egg protein is deaminated.16
— Prolon/FMD limits protein intake to about 20 grams per day. Excess protein intake has been found to suppress autophagy and promote insulin resistance,17 which would undermine benefits from fast-mimicking. For someone whose equilibrium is 2000 calories/day, 20 grams/day may be sufficient to maintain muscle while metabolizing visceral fat. Unfortunately, Prolon is plant-based, and plant-based foods typically have lower protein utilization than most animal-based foods.
— Prolon does supplement branched-chain amino acids — BCAAs — a subset of three of the EAAs. I’ll defer to Ben Greenfield for his discussion of ‘The Unfortunate Side Effects of BCAAs In Isolation”.
— For iFMD, we included foods with relatively high amino acid utilization, viz. pasture-raised eggs, grass-fed lamb, and liver (from pasture-raised/grass-fed chicken, turkey, lamb, beef). When consuming animal protein, it’s important to include non-muscle components in order to improve amino acid balance. We also supplemented (plant-based) EAAs, which deliver nearly 100% utilization. So even though I consumed about 50 grams of protein daily, my ‘aggregate glucose’ — e.g., factoring in gluconeogenesis — was comparable to Prolon/FMD, as evidenced by our blood glucose and ketone test results (reported above at the end of ‘Our Experience’).
— Although we include animal-based food, we still consume a large variety of plant species from whole food sources:18 about 40 different vegetable species, plus several berry, nut and seed species.19
Our iFMD Plant Foods (Copilot generated ‘still life’) Recent research indicates that the number of plant species in your diet is more important for health than the quantity of plant calories consumed.
Fat: Compared to Prolon, I20 reduced carbs and increased fats, making my diet more ketogenic (fat-burning). My typical macronutrient breakdown: 15% carbohydrate, 14% protein, 71% fat.21
— Prolon avoids saturated fat and favors unsaturated fat without distinguishing between omega-3 fatty acids, which are generally anti-inflammatory, versus omega-6 fatty acids, which are generally inflammatory.
— Because Prolon is plant-based, it appears to contain about ten times the amount of possibly obesogenic linoleic acid compared to ancestral diets. Prolon does include a DHA (omega-3) supplement derived from algal oil. We favor foods high in monounsaturated and omega-9 fatty acids — especially macadamia nuts — over foods high in omega-6’s, and do not avoid saturated fat.Ingredient quality:
For iFMD, we primarily prepared meals from whole, organic foods (although we usually include a commercial cracker a day), whereas Prolon/FMD consists of processed foods — a necessity since it’s a packaged product — from conventional (i.e., non-organic) plants.
— For example, we made our own organic vegetable soups with home-made pasture-raised chicken bone broth.22Some of Prolon’s supplements are very low quality. A few examples:
Magnesium oxide has low absorption from the gut — the lowest bioavailability of the 15 forms of magnesium evaluated in this study — and consequently is more likely to irritate the digestive tract than the forms of magnesium that we supplement.
dl-alpha tocopherol (synthetic vitamin E), instead of naturally sourced d-alpha tocopherol.
Silicon dioxide — why supplement sand?
Supplements:
We supplement l-carnitine, which plays a crucial role in transporting fatty acids to mitochondria. Red meat is by far the greatest food source of l-carnitine, omitted in L-Nutra’s plant-based product.
We supplement l-tyrosine and myo-inositol to support thyroid function.
We avoid supplementing antioxidants that suppress autophagy (the reprocessing of damaged cell components). We do continue supplementing astaxanthin, an antioxidant that nonetheless promotes autophagy while promoting fat oxidation.
What’s Next?
In a February cardiology visit, I received an Inbody Body Composition Analysis recommending that I shed 17.4 pounds of body fat. This was the upper end of my own guesstimate of how much body fat I could safely lose. If achieved, from there I could conceivably dehydrate to make my lowest college wrestling weight. Seems far-fetched! Well, I’ll see how far I can get with help from iFMD.
For now, I plan to repeat iFMD once more in April, the time of year when my weight usually peaks:
From May through August, our wilderness canoe trip followed by summer baseball should improve my body composition as they usually do, without need for iFMD. Then reassess after the baseball season ends.
Gretchen plans to use iFMD periodically to bring down inflammation and keep me company.
Additional Resources
Chris Masterjohn, Ph.D., a nutrition scientist I greatly respect, recently wrote a very good guide on How to Lose Fat Without Losing Muscle — subtitle: “NEVER start with cutting food intake!”
I learned about Herman Pontzer’s research from this article. You may (or may not!) find the Experimental Fat Loss newsletter/substack helpful.
Especially with the new GLP-1 agonists such as Ozempic.
In particular, fast twitch muscle can help you maintain balance or reduce impact severity by, for example, grabbing support.
Laugh if you like, but I remember one winter in grad school when I lost enough weight that my butt started hurting when I’d get knocked down taking a charge in basketball.
Now that I’ve published this article, I’ve made clickable links that work when you read the article in a browser. But they don’t work in either the Substack app or in an email.
My edits in brackets and emphases (in bold).
I thought the interview was a Ben Greenfield podcast episode, but I can’t find it.
In addition to muscle loss, and among other things, it also reduces thyroid hormone production and consequently body temperature, which in turn increases risk of infection, not to mention reducing cold tolerance.
Peter Attia, M.D., reports backing off from his rigorous fasting regimen after discovering he had lost substantial muscle mass which had been replaced by visceral fat.
We weren’t as aggressive the third time; more details in footnote 12 below.
Including Gretchen’s gold medal winning performance in the 65-to-69-year-old women’s division at the International Master’s Speed Skating Sprint Games.
I’m pretty sure that I heard the 1% daily figure on an episode of Mike T. Nelson, Ph.D.’s Flex Diet Podcast episode, but I can’t locate the episode, nor the research from which this claim derived.
In our third ‘bout’ — 1/27-31/25 — we were just trying to metabolize some more visceral fat before competing in the Long Track Speed Skating Age Group Pack National championship, so we targeted a 40% calorie reduction — 1800 calories/day for me. This may be too high to produce some of the other benefits of fasting, but allowed me to train hard and still fully recover for the competition.
That is, used for building tissues or molecules such as hormones and neurotransmitters.
In a healthy metabolism, insulin signals to cells that they should absorb glucose from the bloodstream. That makes insulin resistance is a bad thing — it takes more insulin to coax your cells into taking up glucose. What you want, instead, is to increase the sensitivity of your cells to insulin.
Plus at least 10 more vegetable species in the processed foods we ate, primarily from the daily cracker to which we add vitamin D+K2 drops and spread grass-fed butter oil.
Our iFMD organic plant foods include: avocado, broccoli, basil, Brussels sprouts, carrot, cilantro, cocoa (sourced for low heavy metal content), dill, garlic, ginger, bell pepper, green tea, oregano, kale (green, lacinato, red), lemon grass, mushrooms (baby bella, lion's mane, shiitake, blue oyster, …), olive (black, castelvetrano, green, kalamata), onion (green, red, sweet), parsley, radish, seaweed (kombu, wakame), Swiss chard, tomato (vine-ripe, cherry, sun-dried), yam, zucchini; blueberries, raspberries, strawberries; sprouted almonds, brazil nuts, sprouted cashews, macadamia nuts, pecans, pistachios, sprouted pumpkin seeds, sprouted sunflower seeds, sprouted walnuts).
Gretchen stuck closer to the Prolon/FMD macro percentages.
Percentage of total calories.
Interesting that you also got the sleep issues when water fasting. Same for me, although this time it was on day 5. Did you consume any caffeine?
As I understand it iFMD is five days, about once a month. What do you eat the rest of the time?