With more than 70% of Americans overweight or obese, Americans enroll in gyms, online fitness programs, group fitness classes, or purchase exercise equipment with a vision of getting lean and fit (NIDDKD, 2021).  The fitness industry in 2025 was valued at approximately $45 billion (Statista.com, 2025).

Every new year people picture themselves working out hard, getting a fit, lean, muscular, or toned body–if they can just stick with exercising for long enough. If they can just “do enough…” “You don’t need medicine, just work out and eat right…” 

In many cases, significant others who want to support their spouses in their health goals will push them to exercise harder.  “That is not a real workout, you need to (insert exercise prescription here)…”

Because intense exercise requires a lot of effort and discipline, the trade off must be amazing results in terms of body transformation…or so the thinking goes.  However, is losing weight and looking great really as simple as “eating right” and “moving more..?”  

If so, why are many fitness classes filled with sweaty people who show up week after week to grind through vigorous intensity group fitness classes…only to look essentially the same…month after month…sometimes year after year….?  

To be sure, some people attending group fitness classes as part of their health journey do transform their bodies…but why doesn’t everyone?  In fact….why is it that these persons who do transform their bodies during fitness classes tend to be the exception as opposed to the norm?

Is it that everyone else is “lazy,” or not “pushing themselves hard enough?”  Or is there something else going on?  

Curiously, research suggests that physical activity has actually increased between 1980 and 2017…along with the rise in obesity…so clearly activity levels are not directly correlated with the obesity situation in our nation (Mozaffarian et al., 2025).  

What is the role of exercise and activity in promoting weight loss?  How does it help?  What are its limitations?

Research shows exercise alone is insufficient to produce significant weight loss

The research is clear that exercise alone is not enough to produce weight loss (Jian & Villareal, 2025).  A meta-analysis of 34 randomized-controlled trials noted minimal impact of exercise interventions on body weight (O’Donoghue et al, 2021).  

These trials included aerobic exercise, resistance training, and combination training interventions (O’Donoghue et al., 2021).  Weight loss, when it did occur, ranged from 1 to 2 lbs over an average of a 20-week period for the intervention. 

What exercise produced the most weight loss, how much, and in what doses?

Interventions varied in efficacy, with the most effective interventions to least effective interventions for weight reduction listed in order:

• High intensity aerobic training (heart rate greater than 75% max at least 3 times per week for 30-60 minutes) combined with high load resistance training (loads at least 75% of 1 rep max, at least 3 times per week for 30-60 minutes)
• Moderate intensity aerobic training (heart rate 65-75% of max heart rate at least 3 times per week for 30-60 minutes) combined with low to moderate load resistance training (loads of 50-75% of 1 rep max at least 3 times per week for 30-60 minutes)
• Moderate aerobic training without any resistance training
• Vigorous / high intensity aerobic training without any resistance training
• High load resistance training without any aerobic training
• Low to moderate load resistance training without any aerobic training (O’Donoghue et al., 2021)

However, even the most effective training protocols described above involving combination training of high intensity aerobic training paired with high load resisted training produced about 2 lbs of weight reduction on average (O’Donoghue et al., 2021).  

Weight loss methods and effects on lean body mass

The benefits of weight loss are well documented…even relatively small decreases in weight such as a 5% reduction in body weight leads to clinically significant reductions in blood pressure, blood sugar levels, cholesterol, and improves insulin sensitivity (Jian & Villareal, 2025).  In fact, just losing approximately 5 lbs can result in some cases in a reduction of diabetic medications for persons with obesity and diabetes (Jiang & Villareal, 2025).  

However, a significant concern associated with weight loss includes loss of lean body mass including loss in muscle and reductions in bone density (Jian & Viallareal, 2025).  Muscle loss and bone density reductions during weight loss are a concern with all forms of weight loss, and are not just limited to weight loss associated with the use of GLP-1 therapies (Neeland, Linge, & Birkenfeld, 2024). 

Evaluations of lean body mass reduction during weight loss shows the following (Neeland et al., 2024):

• 5.9%-26.1% for weight loss due to nutrition, behavioral, and medication interventions
• 19.3%-23% for weight loss due to weight loss surgical interventions
• 20-50% for weight loss using GLP-1 medications

However, when lean mass losses are tracked based on total weight loss, the lean mass reduction is relatively similar between all methods of weight loss, with GLP-1 lean mass reductions just slightly higher than surgery, and surgery just slightly higher than dietary interventions (Neeland et al., 2024).

It is also noted that lean muscle mass during GLP-1 therapy is highly variable among individuals (Neeland et al., 2024).  Lastly, using current measurement methods, 15% of “lean mass” actually comes from fat tissue.  Therefore, loss of fat tissue will correspond with loss of some “lean mass” using current methods to measure body composition.  

However, for persons who already have low levels of muscle and are at risk for osteoporosis such as older, sedentary individuals, prevention of muscle loss and preservation of bone density is of critical concern during weight loss (Jiang & Viallareal, 2025).  Sarcopenia is a condition of low muscle mass and can occur even in the presence of overweight and obesity–particularly in older clients.

Sarcopenia is characterized by (Neeland et al., 2024):

• Weakness
• Fatigue
• Loss of balance
• Decreases in mobility

Exercise protects lean mass during weight loss, shrinks waist size, and improves body composition

Both aerobic and resistance training support lean body mass retention during weight loss (Neeland et al, 2024).  However, resistance training is more effective at preventing the loss of strength.  

In one randomized-controlled trial lasting 1-year in which elders lost 10% of their body weight using caloric restriction, those in the caloric restriction +  exercising intervention group boosted their physical performance test scores by 21% compared to the control group’s improvement of 12% (Jiang & Dillareal, 2025). 

In another 6-month randomized controlled trial on elders with obesity where a 9% body weight reduction was achieved through calorie reduction, participants were simultaneously randomly assigned to an aerobic, resistance training, or combination training arm (Jiang & Dillareal, 2025).  Outcomes for lean body mass reductions during the 9% body weight reduction were as follows:

• 2% reduction in lean body mass for the resistance training group
• 3% reduction in lean body mass for the combination training group doing aerobic exercise and strength training
• 5% reduction in lean body mass for the aerobic training only group

Protection against lean body mass reduction is critical during weight loss interventions, as restoration of lean body mass once it has been lost is much slower than restoration of body fat (Jiang & Dillareal, 2025).  This is especially important in cases where persons undergo multiple weight loss/ weight regain cycles. 

In a meta-analysis evaluating exercise effectiveness for various outcomes in participants with obesity, waist circumference was reduced by approximately 2 cm on average in participants doing all forms of aerobic exercise and combination resistance training + aerobic exercise, versus 1 cm reduction in persons who did resistance training alone (O’Donoghue et al., 2021).  

Similarly, all forms of exercise programming that included aerobic exercise resulted in lower body fat percentages, though again, effects were small…with the most intensive regimens producing approximately 3% average body fat reduction and the less intensive regimens resulting in approximately 2% average body fat reduction.  

Exercise counters the body’s attempts to stall weight loss, can help prevent regain

An interesting phenomenon has been documented consistently in studies on food intake and activity levels.  When people take in less calories, activity levels also decrease (Westerterp, 2019).  Daily caloric expenditure also decreases.  

In a large study analyzing the effects of caloric restriction,  the Minnesota experiment, the reductions in daily caloric expenditure during a calorie deficit were mostly from reductions in daily activity levels (Westerterp, 2019).  Specifically, nearly 60% of the reductions in daily caloric expenditure were due to drops in daily physical activity.

This is compared to reductions in daily basal metabolic rate explaining just over 30% of reduced daily caloric expenditure, and reductions in digestion of foods equating to a 10% reduction in daily caloric expenditure (Westerterp, 2019).  

What this means is that while metabolism does slow during weight loss due to a variety of factors (your body is smaller, so everything you do including simply existing in a smaller body burns less calories than when you are heavier), the largest reduction in caloric expenditure due to reductions in movement is treatable and reversible (Westerterp, 2019). 

This can be accomplished by intentional movement and activity.  Indeed, current best practices for breaking through a weight loss plateau include increasing frequency, intensity, and duration of exercise in addition to nutrition interventions (Sarwan et al., 2024).  

Resistance training boosts muscle mass, basal metabolic rate, and insulin sensitivity.  Aerobic activity and intentional movement throughout the day eliminate calories–helping to enhance a caloric deficit already achieved using nutrition strategies (Sarwan et al., 2024).  

National guidelines recommend at least 300 minutes of moderate intensity aerobic activity per week for anyone that has lost more than 5% of their body weight and desire to prevent weight regain (U.S. Department of Health and Human Services, 2025).  The guidelines also recommend strength training at least twice per week to further stabilize weight and prevent weight gain.  

General benefits of exercise are awesome regardless of weight impact!

While the effort to reward ratio for weight loss is underwhelming on the surface, the returns on investment in terms of benefits of exercise for overall mental and physical health are incredible!

According to the CDC (2025), the many benefits of exercise include but are not limited to: 

• Lower anxiety immediately after exercise 
• Improved thinking, learning, and judgement capacity as you age
• Lower risk of depression
• Improved sleep and sleep quality
• Improved weight loss WHEN PAIRED WITH NUTRITION strategies and when performed at sufficient levels (300 minutes / 5 hours of moderate intensity activity such as brisk walking per week or the equivalent of this)
• Improved immune function and lower risk of serious infection related outcomes such as hospitalization and death
• Reduced risk of at least 8 different cancers, including kidney, breast, colon, lung, stomach, esophagus, and endometrium cancer
• Reduced premature death from all causes noted at 8,000 to 10,000 steps per day average for adults under 60, and at 6,000 to 8,000 steps per day for older adults
• Decreased arthritic pain for those with arthritis
• Improved blood sugar control for diabetics
• Improved balance, stability, and reduced risk of falls and disability in older adults

Our experiences with weight loss clients over a 5+ year period

While anecdotal, case studies can provide real world examples for how exercise and nutrition interplay to produce desired results. We have worked with many clients who have shifted their nutrition towards higher lean protein intake and higher whole food plant-based food selections.  

Clients who make these nutritions shifts successfully and maintain these shifts consistently do the absolute best out of all clients in achieving deep weight loss (such as 40lbs to 100 + lbs weight loss).  Clients who make these nutrition shifts plus work very active jobs where they are on their feet all day and moving around make the fastest progress.  

For those that do not have active jobs, assuring they are hitting 8-10,000 + steps per day helps them make more rapid progress as long as they have already successfully implemented nutrition recommendations.  However, for clients that hit 8-10,000 steps per day but who have not reduced alcohol intake, and / or have not consistently shifted to very lean protein sources paired with high fiber whole food plant based food sources, the increased steps are not enough to propel continued weight loss.

In other words, exercise compliments nutrition shifts in accelerating weight loss, but is insufficient on its own and is not a replacement for consistent, healthy nutrition choices.  This is why we have had great success in elderly clients who have limited mobility, and have seen busy nursing staff struggle despite their active jobs.  

Nutrition compliance will always be far superior to exercise in producing weight loss.  Exercise is amazing for many reasons, but only serves to compliment a healthy and consistent nutrition pattern.  

Wrap up

Exercise is wholly insufficient to produce meaningful weight loss on its own.  Even the most intense training protocols involving combinations of heavy weight training at least 3 days a week and high intensity cardio sessions lasting 30-60 minutes at 3 days per week produced meager weight loss results when used as a sole intervention.

However, for persons who have made consistent dietary changes across all days of the week, exercise can support weight loss as an accelerant, can help break past plateaus, and can prevent weight regain after losing weight.  

Beyond this, exercise supports mind and body health by reducing depression and anxiety, lowering death rates from all causes including heart disease and cancer, prevent falls and frailty in elders, and preserve lean body mass during weight loss.  

The dose matters:  300 minutes (5 hours) of brisk walking per week or its equivalent are necessary for most individuals who want to maintain a weight loss greater than 5% of their body weight, along with 2 total body strength sessions per week to preserve lean muscle mass.

How we can help

We have coached hundreds of clients for more than 5 years, helping them to make dietary overhauls along with helping them to adopt healthy movement habits appropriate for their health and ability levels.  

If you are serious about making changes to your weight and health, doing it on your own can often feel defeating.  Having a team supporting you and addressing underlying medical issues can make a major difference in your odds of achieving your ultimate goals.

Give us a call at 717-297-7900 to schedule a free consultation today!!

Written by Donovan Carper MSN RN CPT CHC

References 

CDC. (2025, December 4). Benefits of physical activity. Retrieved from https://www.cdc.gov/physical-activity-basics/benefits/index.html 

Jiang, B. C., & Villareal, D. T. (2025). The Benefits of Exercise Training in Combination With Weight Loss Therapies. Diabetes, 74(12), 2199–2206. https://doi.org/10.2337/dbi25-0001 

Mozaffarian, D., Agarwal, M., Aggarwal, M., Alexander, L., Apovian, C. M., Bindlish, S., Bonnet, J., Butsch, W. S., Christensen, S., Gianos, E., Gulati, M., Gupta, A., Horn, D., Kane, R. M., Saluja, J., Sannidhi, D., Stanford, F. C., & Callahan, E. A. (2025). Nutritional priorities to support GLP-1 therapy for obesity: A joint Advisory from the American College of Lifestyle Medicine, the American Society for Nutrition, the Obesity Medicine Association, and The Obesity Society. Obesity (Silver Spring, Md.), 33(8), 1475–1503. https://doi.org/10.1002/oby.24336 

National Institute of Diabetes and Digestive and Kidney Diseases (NIDDKD). (2021). Overweight & obesity statistics. Retrieved from https://www.niddk.nih.gov/health-information/weight-management/adult-overweight-obesity/definition-facts 

Neeland, I. J., Linge, J., & Birkenfeld, A. L. (2024). Changes in lean body mass with glucagon-like peptide-1-based therapies and mitigation strategies. Diabetes, obesity & metabolism, 26 Suppl 4, 16–27. https://doi.org/10.1111/dom.15728 

O’Donoghue, G., Blake, C., Cunningham, C., Lennon, O., & Perrotta, C. (2021). What exercise prescription is optimal to improve body composition and cardiorespiratory fitness in adults living with obesity? A network meta-analysis. Obesity reviews : an official journal of the International Association for the Study of Obesity, 22(2), e13137. https://doi.org/10.1111/obr.13137 

Sarwan, G., Daley, S. F., & Rehman, A. (2024). Management of Weight Loss Plateau. In StatPearls. StatPearls Publishing. Retrieved from https://www.ncbi.nlm.nih.gov/books/NBK576400/ 

Statista.com. (2025). Key figures on the fitness, health and gym club industry in the United States as of May 2025. Retrieved from https://www.statista.com/statistics/605223/us-fitness-health-club-market-size-2007-2021/?srsltid=AfmBOoo9E6O2L2QLJ_ImdmiwVcBlR0d-Ecsa4HezI5sQlm2EMgl__PHm 

U.S. Department of Health and Human Services. (2025). Physical activity guidelines. Retrieved from https://odphp.health.gov/sites/default/files/2019-09/Physical_Activity_Guidelines_2nd_edition.pdf

Westerterp K. R. (2019). Physical activity and body-weight regulation. The American journal of clinical nutrition, 110(4), 791–792. https://doi.org/10.1093/ajcn/nqz132