By Cody Haun, PhD, MA, CSCS.
How To Maximize Fat Loss & Minimize Muscle Loss
Loss of body fat tissue readily occurs when the body is faced with a sustained energy, or calorie, deficit. A calorie deficit can be defined as the intake of a lower number of calories than the amount required to sustain your body’s current energy stores. Your body stores energy primarily in the form of fat tissue, in cells called adipocytes (i.e., fat cells). Although some fat is stored intramuscularly, most fat is stored in lipid droplets housed within fat cells. Of particular importance when seeking to lose body fat, subcutaneous fat cells (i.e., the fat you can pinch just beneath the skin) can be broken down and used for energy during exercise or at rest. Consequently, exercising at an appropriate dose, and creating the physiological scenario at rest to augment fat loss are two primary ways to lose body fat. However, too much exercise and an excessive calorie deficit can result in unnecessary and undesirable losses in lean body mass (e.g., muscle tissue). So, how do we calculate the appropriate energy deficit to maximize fat loss while minimizing losses in lean body mass?
First, it’s important to calculate the amount of energy you expend at rest (i.e., resting metabolic rate or RMR). Although more advanced equations can allow for more accurate calculations, generally, multiplying your bodyweight in pounds by 11 can get you pretty close to the true value (e.g., RMR = 200 x 11 = 2200 calories). Figuring out how much of a deficit is warranted to maximize fat loss while minimizing lean tissue loss is primarily related to: a) how much energy you expend, and b) how much energy you consume.
How much energy do you expend?
It is helpful to start with this equation to direct the discussion that follows.
RMR + NEE + EE = TDEE
Resting metabolic rate (RMR) is the amount of energy expended at rest while not actively digesting food (RMR).
Non-exercise energy expenditure (NEE) is composed of the thermic effect of food (TEF) and non-exercise activity thermogenesis (NEAT). Excluding odd macronutrient meal compositions, estimating the TEF at ~10% of total energy consumed for the day is reasonable (e.g., 2000 calories consumed x 10 % = 200 cal. TEF).
Here are some helpful coefficients to clarify how much total energy you expend on a daily basis outside of intentional exercise (i.e., NEAT) based on how active you are:
Sedentary (hardly any activity): RMR x 1.1
Light Daily Activity: RMR x 1.4
Moderate Daily Activity: RMR x 1.7
Heavy Daily Activity: RMR x 2.0
So, NEE can be calculated by summing an activity-adjusted RMR and the TEF (e.g., activity-adjusted RMR + TEF = NEE).
Energy expenditure from exercise (EE) is the amount of energy expended from exercise beyond resting values.
Although certain activity coefficients for estimating energy expenditure during exercise exist, a more evidence-based method of calculating expenditure can provide more accurate estimations. Below, you’ll find a small section of the Soma Nutrition & Recipe Ebook along with calculations for certain exercise intensities based upon a specific bodyweight to help you make these calculations.
Next, you’ll need an approximation of how many calories you expend from exercise (EE) or training. Tracking via wearable technology of calories expended beyond rest can help with this calculation. A MET is a metabolic equivalent. This is equal to ~1 kcal/kg of body mass/hour, or ~3.5 ml of O2 consumed/kg/min. So, you’ll need to know the amount of time, expressed as an hour, your body mass in kg, and the information from the table below to make this estimate.
For example, let’s say you weigh 220 lbs. Your body mass in kg is 100 kg (220/2.204=100).
You’re ~30 years old and, generally speaking, a healthy person.
Therefore, your VO2max, as shown in the table, is probably ~12 METS or ~40 ml/kg/min.
If you exercise at a moderate intensity for 30 minutes (i.e., 0.5 hours), you’re MET estimate for that period of time is ~6 METS. Recall that a MET is ~1 cal/kg/hr. So, you’d be expending ~6 cal/kg/hr, which, in this example, is 600 calories expended per hour (i.e., 6 x 100/0.5. Since you’d be otherwise resting, let’s subtract 100 calories from the calculation (i.e., 1 MET). Consequently, you’ve expended ~200 calories beyond resting values from exercise. This information can be used to guide setting up calorie intakes on various days of the week wherein you are either resting or training. It’s also relevant to factor in what is known as the thermic effect of food (TEF), which is essentially the energetic cost of digesting and absorbing the food you eat. Although different for each macronutrient, particularly for protein, this value tends to be ~10 % of the calories you consume on a daily basis.
Clarifying these values can allow you to calculate your total daily energy expenditure (i.e., TDEE). Once this value is known, it becomes much easier to clarify how much energy you should consume in the form of food to result in fat loss.
How much should you consume?
To make this value more accurate, first, estimate your body fat percentage. Here are some photos to aid in this estimation:
Once you have selected the photo you feel is most representative of your body fat percentage, calculate the absolute amount of fat you possess by multiplying your bodyweight in lbs by the estimated percentage (e.g., 200 lbs x .15 = 30 lbs of body fat).
A study published in 2003 in the Journal of Theoretical Biology suggests that ~30 calories per pound of body fat can be broken down and used for energy at rest in a 24 hour period. Based on the above 200 lb.-person example at 15 % body fat, this translates to ~900 calories. Subtracting 900 from 2200 (i.e., RMR) results in a suggested calorie net of 1300 calories. Notably, this assumes a sedentary lifestyle and no additional energy expenditure from exercise. Due to the thermic effect of food (i.e., ~10 % of calories consumed), this suggests that near maximal losses of body fat at rest, without severe reductions in lean tissue, could occur at an intake of ~1500 calories for this hypothetical 200 lb. individual.
Now, we must consider ways in which insurance can be provided for avoiding losses in lean body mass and how exercise can affect these calculations.
Low intensity, steady-state exercise is primarily fueled by the oxidation of fat for energy. Furthermore, this increased fuel use during exercise can increase the breakdown of body fat significantly more than deficits created by the diet alone. That is to say, one can lose significantly more body fat in a sufficiently large unit of time (e.g., weeks, months) when exercising and creating a dietary deficit compared to a dietary deficit alone. So, fat loss can be augmented by the addition of low-intensity cardio each day or a few times per week for between 10-60 minutes of sustained movement. However, without an unambiguous signal to the body and particularly to muscle tissue to maintain lean tissue amounts via resistance training, the risk of losing lean tissue increases in this scenario. Fortunately, two distinct stimuli to preserve muscle tissue when faced with a calorie deficit are: a) resistance exercise, and b) relatively high dietary protein intake.
A recent study from Dr. Stuart Phillips laboratory suggests that an intake of 2.4 g/kg of body mass (i.e., ~ 1.2 g/lb of bodyweight) can defend lean tissue mass sufficiently during a hypocaloric diet (i.e., an energy deficit). Furthermore, defense of lean body mass, and even a potential increase in lean body mass, can be realized by the addition of resistance training with as few as three sessions per week. This study brilliantly illustrates the power of sufficient protein intake and resistance training to defend lean tissue mass while dieting.
“Practically, training intelligently with weights and eating sufficient protein serves to antagonize diet-induced muscle loss.”
Importantly, clarifying the specific amount of calories and protein to consume, and the appropriate dosage of both cardio and resistance training can become more complicated the more lean someone is or more body fat an individual possesses when beginning a dietary and training intervention. In my opinion, this is why hiring a qualified coach to help you get started, or to work with for the long-term, can be so helpful. This can allow you to avoid misapplication of this information and expedite the results you desire. Also, providing general recommendations of training dosages and programming can be problematic since we’re all different. Consequently, in this blog, I stray away from specific recommendations regarding training and nutrition dosing and would rather point you toward a qualified coach in your area. Notwithstanding, the calculations required to clarify the amount of energy to consume on a given day in which you have an idea of how much energy you are expending are rather straightforward. To review, calculate your TDEE by first calculating your RMR (corrected for daily activity) and estimate the amount of energy you expect to expend during exercise. Then, consuming ~500 calories below this value per day is reasonable for getting started. Notably, these calculations are not static, and must be altered as your energy expenditure from exercise changes, and your bodyweight changes. For a more aggressive approach, you can calculate the minimum recommended amount based on the information discussed above. Recall, that calculation involved the estimation of body fat and the calorie coefficient per pound of body fat which are then used to estimate approximate maximum fat loss rates at rest. It seems logical that netting no less than this amount each day better ensures that lean tissue is defended. Based on the 200 lb. individual example above, this would be no less than ~1500 calories per day. To summarize some of the key points, adding a modest amount of low intensity cardio a few times per week, at least two resistance training sessions, and consuming ~1 g of protein per pound of bodyweight are sound strategies for maximizing fat loss while minimizing muscle loss. However, the first thing to calculate and consider is TDEE, and the selection of a value that doesn’t exceed the deficit calculated for the net minimum value discussed above. To be clear, the calorie calculation is the primary variable to attend to first, then, the protein and training strategies serve to ensure the loss in bodyweight is primarily fat tissue. Try and not create too much of an energy deficit too soon. I’d suggest beginning more conservatively (i.e., ~500 calories less than estimated TDEE) and fine-tuning energy expenditure and consumption values based on closely monitoring your bodyweight during the first few weeks of beginning your fat loss program.
Best wishes on your training endeavor and feel free to contact me with any questions.
“I am a scientist first and a coach second. I have a passion for positively impacting the lives of people through providing critically thought-out, data-driven, scientifically-sound nutrition and training programming services that equip individuals to successfully achieve their performance and/or physique goals. I seek to offer the best service within my power and I am confident, given my background, education, experience, and relentless pursuit of knowledge pertaining to human physiology and the training process, that I can provide you with programming to realize great results. Feel free to contact me with any questions.”
Cody Haun, PhD, MA, CSCS
-APLYFT Science Consultant