By: Eric Trexler, PhD
Many lifters engage in repetitive bulk-and-cut cycles. Others do one major bulk, then attempt to cut down and maintain a lean physique for the long run. In either case, an inflection point is reached – the point where you are satisfied with the muscle mass you’ve cultivated, but eager to shed the fat to reveal a lean, muscular physique. This is a logical, systematic approach to physique improvement, but it has one key vulnerability: excessive muscle loss during the cutting phase.
But how much muscle loss should you expect? And what can you do to minimize the degree of muscle loss? This article will address those critical questions (and more).
Loss of Muscle Mass While Dieting
Many common methods of body composition measurement, including BodPod, skinfold calipers, and the bioelectrical impedance technology in your bathroom smartscale, separate the body into two components: fat mass and fat-free mass. Fat mass is exactly what it sounds like – the portion of your body that is fat. Fat-free mass accounts for everything else, including muscle, skin, organs, bones, and even water. It’s commonly said that humans lose about 25% of their weight as fat-free mass. For example, if you lost 20 pounds of total weight, this common heuristic suggests that 5 of those pounds would be fat-free mass, and the other 15 pounds would be fat mass.
If this number seems overly simplistic to you, you’re not alone. A 2014 paper by some pretty major names in body composition research criticized this heuristic, and their critique is pretty hard to disagree with. As they put it: “the proportion of weight loss as lean tissue varies over time and is determined by multiple factors including level of energy intake, diet composition, sex, baseline adiposity, the presence of inactivity or type and level of added activity, and potentially the subject’s metabolic state or hormonal response.” Of course they’re correct, but at the end of the day, heuristics are intended to represent the “typical” or “average” response, not a universally true response for all people and circumstances.
Nonetheless, there’s another huge issue with this 25% number: it refers to fat-free mass, not muscle. Muscle certainly represents a large portion of fat-free mass, but it’s only one component of many. Most lifters and fitness enthusiasts are specifically concerned about muscle loss rather than the loss of fat-free mass. Fortunately, recent research sheds some light on actual muscle loss (rather than fat-free mass) during weight loss diets.
A recent paper combined data from two different weight loss studies that both used MRI, the gold standard for body composition assessment. By analyzing MRI scans from nearly 900 weight loss study participants, they concluded that males lost about 22% of their weight as muscle mass, whereas females lost about 11%. These data confirm that a large portion, but certainly not all, of the weight lost as fat-free mass is actually muscle tissue. The data also suggest that males tend to lose more muscle than females – specifically in studies where participants have plenty of fat to lose and are not lifting weights.
But What About Jacked People?
The circumstances of the typical RP reader are far different than those of the typical weight loss study participant. Those studies typically recruit people with obesity who are not exercising and have no recent history of regular resistance training. They are different across many key domains – body fat, muscularity, training experience, exercise habits, and dietary habits, among others.
While we don’t have a ton of research documenting longitudinal changes in body composition among lifters who are legitimately jacked, we do have some evidence in physique athletes to lean on. Broadly speaking, the evidence from bodybuilders indicates that the relative proportion of fat-free mass loss during diet is similar or slightly larger than the typical 25% heuristic. While some case studies report values below 25% and others report values above 50%, the 25-35% range seems to be fairly typical. We can safely assume that a decent chunk of this fat-free mass is muscle tissue.
In other words, it seems that jacked people who are trying to get shredded lose about as much, or slightly more, fat-free mass (and muscle) than the typical weight loss study participant. This is despite the fact that they’re competitive physique athletes who are actively engaged in strenuous resistance training programs and eating high-protein diets. But what’s striking about the physique athlete data is the variance in outcomes. If I told you that you can expect to lose 20-60% of your weight as fat-free mass, you probably wouldn’t find that information very helpful. Losing 60% would feel like a botched cut, while losing 20% would seem like a fantastic outcome. But where there is variance there is opportunity. The wide range of observed results gives us strong reason to believe that we can leverage some key strategies to take our fate into our own hands, nudging ourselves in the direction of more fat loss and less fat-free mass loss.
Minimizing Muscle Loss
While we don’t have in-depth research on the matter, years of experience make me quite confident that your genetics will dictate some of your success in terms of gaining muscle and retaining it during a cut. But since your opportunity to select your parents has come and gone, we’ll focus on some more actionable factors that may help you keep your hard-earned muscle during your next cut.
Select An Appropriate Body-Fat Target
Research dating back to the 1980s suggests that the composition of your weight loss depends, to some extent, on your current body-fat level. We see this all the time in resistance training research. When a group of people with 40% body-fat begin a resistance training program, “recomposition” (that is, simultaneous fat loss and muscle gain) is the norm. But your hopes of recomping at 5% body-fat are about as viable as building a snowman in hell. As we get leaner, the likelihood of muscle loss increases, which is almost certainly why physique athletes often lose more than 25% of their weight as fat-free mass during contest preparation.
So, be sure to choose your body-fat target wisely. For many people, getting to 12% body-fat is a feasible goal that will reveal plenty of muscle definition and virtually maximize the health benefits of leanness, without dramatically inflating the loss of fat-free mass or causing some of the hormonal consequences associated with extreme leanness. Having said that, I totally understand that it’s sometimes necessary to get as shredded as humanly possible. Just understand that as the final body-fat target gets more and more ambitious, the likelihood of muscle loss, particularly toward the tail-end of the cut, grows accordingly.
Take Your Time With Weight Loss
Once you decide where you’re trying to go, your next decision is how long you’ll take to get there. This is an important decision because your deadline determines your rate of weight loss, and your rate of weight loss determines how large your caloric deficit will be.
Research has shown pretty clearly that your prospects for gaining (or retaining) fat-free mass, including muscle, can be impacted by the size of your calorie deficit. In resistance training studies, deficits greater than 500 kcal/day make it challenging to gain muscle mass, and the larger your deficit gets (beyond 500 kcal/day), the greater the likelihood of actual muscle loss.
Image courtesy of MASS Research Review, massresearchreview.com
To set yourself up for success, take your time with your weight loss. A decent heuristic for keeping your weight loss on track without too aggressive of a deficit is to aim for about a pound of weight loss per week. If you have relatively high body-fat, you can certainly get away with 1.5 pounds per week toward the beginning of your cut. You might also consider shifting down to only 0.5 pounds per week toward the end of the cut when your body-fat is very low. But when you’re at “cruising altitude” for the majority of your cut, a pound per week keeps your energy deficit in a manageable range without stretching out your timeline to an unnecessary degree.
Eat Enough Protein
We all know that protein is important for building and retaining muscle. We can execute the perfect training program to stimulate maximal levels of muscle protein synthesis, but it’s all for naught if we don’t actually have the amino acids available to build new muscle proteins. Under normal circumstances, you’ll often hear that eating 1.6 to 2.2 grams of protein per kg of body mass (g/kg) is sufficient for maximizing muscle growth. However, research indicates that protein needs are elevated during weight loss diets – especially if you’re already fairly lean.
With support from RP, we (me, Dr. Martin Refalo, and Dr. Eric Helms) recently conducted an updated meta-analysis of protein needs for lean, resistance-training dieters. In line with prior research, we found that higher protein intakes facilitate better retention of muscle. For the average person (that is, non-athletes who can afford a little bit of muscle loss), 1.9 g/kg is a reasonable protein target. But when muscle retention is of the utmost importance, our data suggest that increasing intakes as high as 3.2 g/kg may confer additional benefits.
Relationship between daily protein intake and preservation of fat-free mass during weight loss diets
Notably, this might not actually involve a major change during a cut. If you lose weight while keeping your absolute protein intake stable, then your relative intake (grams of protein divided by current body weight) will gradually increase as the diet continues. So, if you begin your cut at 2.2 g/kg and keep your absolute protein intake stable (or make a few small increases along the way), you’ll be right in line with the evidence.
Ease Up on the Cardio
A little bit of cardio is great for your health. If your cardiorespiratory endurance is so poor that you’re struggling to recover from set-to-set, a little extra cardio might even improve your gains. But when it comes to losing weight, leaning heavily on cardio is a bad plan. First and foremost, the effects of high-volume cardio on weight loss are overrated, and you’ll find that dietary adjustments are a far more efficient route to weight loss. In addition, very large amounts of cardio may interfere with your strength in the gym, especially if you’re struggling to recover in time for your lifting sessions.
In terms of recommendations, cardio guidelines for someone on a cut are similar to the guidelines you’d give your uncle or grandmother: find some physical activities you enjoy, and at the bare minimum, do enough cardio-type activity to leverage its general health and cardiovascular health benefits. On paper, this would look like at least 150 minutes of “moderate” activity per week (that is, anything at the intensity of a brisk walk or higher), or at least 75 minutes of “vigorous” activity per week (that is, anything at the intensity of a jog or higher), or some combination of the two.
You could easily double this target without significantly threatening muscle retention, but you don’t want to inadvertently turn your weight loss phase into marathon training. To err on the side of caution, try to time your cardio strategically by either doing your more substantial cardio sessions on your off-days from lifting, or by separating your cardio and lifting sessions by at least six hours. If you do need to combine your lifting and cardio into the same session, lift weights first and save the cardio for the end.
Make Room for Carbs
There’s no avoiding it – when you’re cutting, the calorie reductions have to come from somewhere. You certainly aren’t slashing protein, so that leaves you with two options: carbohydrate or fat. When it comes to simply losing fat, you can go either direction and have similar levels of success. But if your goal is to maximize muscle retention, I advocate for making as much room for carbs as you can.
You might have heard people saying that lifting weights isn’t very carb-dependent. In most cases, people making this claim are misinterpreting prior research indicating that muscle glycogen only drops by about 25-40%. The implication is that glycogen depletion doesn’t become an issue until you “run out” (i.e., 90-100% depletion of total muscle glycogen). There are a few complicating factors to keep in mind. First and foremost, glycogen depletion becomes a much more pertinent issue when you’re in a calorie deficit, so the research on weight-stable participants doesn’t perfectly translate. Second, there are three distinct glycogen storage depots within muscle tissue. When it comes to producing muscle force, the “intramyofibrillar” depot is most important. Unfortunately, it’s also the first one to deplete during resistance training.
As a result, even modest levels of total muscle glycogen depletion can cause large enough drops in intramyofibrillar glycogen to negatively impact performance in the gym. When you compound this session after session, week after week, all while in a persistent calorie deficit, the cumulative impact on training quality can threaten your ability to maximize muscle retention. So, I try to keep my carbohydrate intake at or above 4 g/kg as long as I can during a cut. When that’s no longer possible, I drop my fat intake as low as 0.5 g/kg to make as much room for carbohydrate as I feasibly can. You might also consider implementing some high-carb refeeds the day before key workouts if there’s a specific muscle group you’re intent on prioritizing.
Conclusion
If you’re trying to get absolutely shredded, some degree of muscle loss is inevitable. But that doesn’t mean you’re powerless – by leaning on some foundational, science-backed strategies, you can stack the deck in your favor and preserve more of your hard-earned muscle. By setting a realistic body-fat goal, patiently applying a conservative energy deficit, eating plenty of protein, resisting the temptation to add tons of cardio, and emphasizing carbs in your diet, you set yourself up with the best chances to retain muscle as you shed fat.
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Eric Trexler, PhD
IG: @trexlerfitness
Website: massresearchreview.com