A Coaching Perspective on the Constrained Energy Model
Why More Cardio Isn't the Answer
As coaches, we have all encountered the client who seems to defy the laws of thermodynamics. They are eating a low-calorie diet, logging hours on the treadmill each week, yet their weight loss has completely stalled. The traditional "calories in, calories out" model tells us that we simply need to increase their output or decrease their input further. However, a recent study by Pontzer and Trexler provides a compelling biological explanation for why this approach often fails and why we need to rethink how we program activity for our clients .
In their paper "The evidence for constrained total energy expenditure in humans and other animals" published in Current Biology, the authors challenge the traditional additive model of energy expenditure. The additive model assumes that physical activity simply adds on top of our baseline metabolic rate. If you burn 300 calories running, your total daily energy expenditure increases by 300 calories. The constrained model, however, proposes that the body compensates for increased physical activity by reducing energy expenditure in other areas, thereby maintaining total energy expenditure within a narrow range.
The Reality of Energy Compensation
The findings from this study are eye-opening for anyone in the fitness and coaching industry. When researchers examined human aerobic exercise interventions, they found that total daily energy expenditure increased by only about 30% of the change expected from additive models. This means that if a client does a cardio session that their smartwatch says burned 500 calories, their actual net increase in daily energy expenditure might only be around 150 calories. The body claws back the rest by downregulating basal metabolic rate, sleeping metabolic rate, and potentially non-exercise activity thermogenesis.
This compensation effect becomes even more pronounced when we look at the specific variables that coaches manipulate daily. The study found that energy compensation is amplified when aerobic exercise is paired with diet restriction. In animal experiments involving dietary restriction, compensation was generally around 100%. Conversely, the research indicated that compensation appeared to be reduced with resistance training.
Activity Variable
Compensation Effect
Coaching Implication
Aerobic Exercise
High (~70% of expected burn is compensated)
Do not rely on cardio as the primary driver of an energy deficit.
Resistance Training
Reduced compensation
Prioritize lifting, as the energy expended is less likely to be offset by metabolic downregulation.
Exercise + Caloric Restriction
Amplified compensation (approaching 100% in some models)
Be extremely cautious when aggressively cutting calories while simultaneously driving up cardio volume.
Clinical Applications in Coaching
Understanding this constrained model fundamentally changes how we should approach programming, particularly for fat loss and contest prep clients. Here are three clinical examples of how this research translates into practice.
Example 1: The Contest Prep Plateau
Consider a male physique competitor who is eight weeks out from a show. His weight loss has stalled, so the initial instinct might be to add another 30 minutes of steady-state cardio to his daily routine while keeping his calories low. According to the constrained model, because he is already in a state of dietary restriction, his body is primed for maximum energy compensation. Adding that cardio will likely result in a near 100% compensation effect. His basal metabolic rate will drop further, he will become more lethargic throughout the day, and his total daily energy expenditure will remain virtually unchanged.
Instead of pushing the cardio lever harder, a better coaching decision would be to implement a strategic refeed or diet break to alleviate the dietary restriction signal, or to focus on maintaining non-exercise activity thermogenesis through step targets rather than adding intense aerobic sessions.
Example 2: The General Population Fat Loss Client
A general population client comes to you wanting to lose 20 pounds. Their previous approach was to run three miles every day while eating a restrictive diet, which worked initially but led to a rapid plateau and burnout. We now know that their body was aggressively compensating for those daily runs.
The coaching application here is to shift the focus toward resistance training. Since the study notes that compensation appears to be reduced with resistance training, we can build a more robust metabolic engine. By prescribing three to four days of resistance training and using moderate step counts rather than intense aerobic work, we minimize the body's compensatory mechanisms while still driving a deficit through diet.
Example 3: The Post-Diet Recovery Phase
When a client finishes a fat loss phase or a competition season, the goal is to restore their metabolic rate and hormonal health. The constrained model shows us that basal and sleeping metabolic rates are downregulated to compensate for high activity. If we simply add food back into their diet but keep their cardio volume high, we are still sending a strong signal for energy compensation.
To truly recover a client's metabolic capacity, we must pull back on the aerobic activity simultaneously with increasing calories. This dual approach removes the demand that is forcing the body to constrain its energy expenditure, allowing basal metabolic rate to recover more efficiently.
Rethinking the Caloric Deficit
The research by Pontzer and Trexler does not invalidate the laws of thermodynamics, but it does highlight the incredible adaptability of the human body. As coaches, we must stop viewing the body as a simple calculator where we can endlessly add output and subtract input.
When we understand that the body operates on a constrained energy budget, we become more strategic. We prioritize resistance training for its favorable metabolic profile. We use cardio sparingly and intentionally, knowing its true energetic cost is far lower than what the treadmill display suggests. Most importantly, we respect the body's compensatory mechanisms and program in a way that works with human biology rather than constantly fighting against it.
Common Client Scenarios and What to Do
The following section is designed as a practical reference for coaches. Each scenario describes a situation you will inevitably encounter, explains what is happening through the lens of the constrained energy model, and provides a clear course of action.
Scenario 1: "I'm doing an hour of cardio every day and I've stopped losing weight."
What's happening: The client's body has fully compensated for the aerobic activity. Their basal metabolic rate and non-exercise activity have both declined to offset the cardio expenditure. They are likely also experiencing increased fatigue, reduced spontaneous movement throughout the day, and possibly disrupted sleep.
What to do: Reduce cardio to three sessions per week at moderate intensity. Replace two of the dropped sessions with resistance training. Introduce a daily step target of 8,000 to 10,000 steps to maintain NEAT without triggering the same compensatory response as structured cardio. Reassess caloric intake to ensure the deficit is being created primarily through nutrition rather than excessive activity.
Scenario 2: "I'm eating 1,200 calories and doing fasted cardio but the scale won't move."
What's happening: This client is experiencing the worst-case combination identified in the research. They are pairing aggressive caloric restriction with aerobic exercise, which amplifies energy compensation toward 100%. Their metabolic rate has cratered, and nearly every calorie they attempt to burn through cardio is being recouped through metabolic downregulation.
What to do: This client needs a reverse diet or structured diet break before continuing their fat loss phase. Increase calories by 100 to 200 per week while simultaneously reducing fasted cardio. Once calories are at a more sustainable level (closer to estimated maintenance minus 300 to 500), reintroduce a modest deficit with resistance training as the primary exercise modality. The goal is to restore metabolic rate before attempting further fat loss.
Scenario 3: "I want to lose weight but I hate lifting weights. Can I just do group fitness classes?"
What's happening: Group fitness classes are predominantly aerobic in nature. While they have psychological and adherence benefits, the constrained model tells us that the caloric cost of these sessions will be substantially offset by metabolic compensation over time.
What to do: You do not need to eliminate what the client enjoys. Keep two to three group fitness sessions for adherence and mental health, but add two days of resistance training as non-negotiable. Frame the resistance training as the tool that builds the body composition they want, while the group classes serve their social and enjoyment needs. Educate them that the calorie burn displayed on their heart rate monitor after a spin class is not translating one-to-one into fat loss.
Scenario 4: "I just finished my show/photoshoot. How do I get my metabolism back?"
What's happening: After an extended period of caloric restriction combined with high training volumes, the client's basal and sleeping metabolic rates have been significantly suppressed. If they simply add food back while maintaining their prep-level cardio, the constrained model predicts that compensation will persist because the high activity signal is still present.
What to do: Implement a structured recovery protocol that addresses both sides of the equation simultaneously. Reduce cardio by 50% in the first two weeks, then continue tapering to minimal levels (two to three short sessions per week at most). Increase calories aggressively in the first two weeks (500 to 700 above contest intake) and then gradually thereafter. Maintain resistance training volume but reduce intensity slightly to support recovery. Monitor biofeedback markers such as sleep quality, libido, mood, and energy levels as indicators of metabolic restoration.
Scenario 5: "My client is a busy professional who can only train three days per week. How do I maximize fat loss?"
What's happening: Limited training availability actually works in our favor here. With only three sessions per week, we are unlikely to trigger the aggressive compensation seen with daily aerobic exercise.
What to do: Program all three sessions as resistance training with short rest periods to maintain an elevated heart rate throughout. Create the caloric deficit primarily through nutrition. Prescribe a daily step target that the client can accumulate through walking meetings, parking further away, or taking stairs. This approach avoids the compensation trap entirely because the activity stimulus is moderate, resistance-focused, and spread across the week rather than concentrated in daily cardio bouts.
Scenario 6: "My client's weight loss was great for 8 weeks but has completely stalled at week 12."
What's happening: The initial weeks of a deficit often show strong results because the body has not yet fully adapted. By week 12, compensatory mechanisms are in full effect. The client's metabolic rate has adjusted downward, their NEAT has likely decreased without them realizing it, and the effective deficit has narrowed considerably.
What to do: Implement a one to two week diet break at estimated maintenance calories while maintaining training. This temporarily relieves the restriction signal and can partially restore metabolic rate. After the break, resume the deficit but consider reducing cardio volume if it has crept up, and ensure the client is hitting their step targets to maintain NEAT. If the client was already at high cardio volumes, reduce them and rely more heavily on the nutritional deficit going forward.