GLP-1 Weight Loss Needs a Nutrition and Strength Prescription
GLP-1 Weight Loss Needs a Nutrition and Strength Prescription
How to Protect Muscle, Nutrient Status, Hydration, Digestion, and Long-Term Function While Using Semaglutide or Tirzepatide
GLP-1 medications have changed the conversation around obesity, diabetes, appetite regulation, and metabolic health. For many people, medications such as semaglutide and tirzepatide reduce persistent hunger, quiet food cravings, improve blood-sugar regulation, and make meaningful weight loss possible after years of frustration.
These are not insignificant benefits. In the SELECT cardiovascular outcomes trial, semaglutide reduced major cardiovascular events among adults with overweight or obesity and established cardiovascular disease who did not have diabetes. This reminds us that GLP-1 therapy is not simply a cosmetic intervention. For appropriately selected patients, it can be an important part of medical care.
But appetite suppression is only one part of the story.
When someone begins eating substantially less, the body does not automatically preserve every gram of protein, fiber, fluid, iron, calcium, vitamin D, vitamin B12, magnesium, and other nutrients. Smaller meals can still be highly nutritious, but only when those meals are planned with intention.
At Health and Exercise Prescriptions®, I believe medication-supported weight loss should be paired with a personalized nutrition, strength, mobility, hydration, digestion, and recovery prescription.
The goal should not be merely to become lighter. The goal should be to emerge from the process stronger, more mobile, metabolically healthier, and better prepared to maintain the results.
What GLP-1 Medications Change
GLP-1 receptor agonists mimic the effects of a hormone involved in blood-sugar regulation, appetite, fullness, and digestion. They can increase glucose-dependent insulin release, reduce glucagon, slow stomach emptying, and influence appetite-regulating areas of the brain. These effects help people feel satisfied with smaller amounts of food.
For many people, this can create a valuable opening for healthier change.
However, reduced appetite can also mean reduced intake of:
Protein
Vitamins and minerals
Fiber
Fluids
Essential fats
Total energy needed for recovery
Nausea, vomiting, constipation, diarrhea, reflux, early fullness, or food aversions may further reduce dietary variety. This is why a medication that reduces appetite should not be treated as a complete health plan by itself.
Tom Malterre’s Perspective: Are GLP-1 Medications Creating Nutrient Deficiencies?
Tom Malterre, MS, CN, IFMCP, is a Bellingham-based functional nutrition and functional medicine educator. He is an Institute for Functional Medicine faculty member, a certified functional medicine practitioner, and the author or co-author of several nutrition books, including The Elimination Diet.
In his recorded webinar, “Are GLP-1 Medications Creating Nutrient Deficiencies?”, Tom raises a question that deserves more attention:
What happens when people eat less, experience changes in digestion, and continue losing weight for months or years?
His presentation explores appetite suppression, digestive changes, nutrient intake, body composition, muscle loss, symptoms that may suggest nutritional imbalance, and laboratory findings observed in clinical practice.
Tom’s central concern is reasonable: when food intake decreases significantly, some people may no longer consume enough of the nutrients required to support muscle, energy production, blood formation, bone health, immune function, digestion, and recovery.
That does not mean every person taking a GLP-1 medication will become deficient. It means that nutrition should be evaluated rather than assumed.
Testing, Laboratory Work, and Diagnostic Insight
One of the strongest parts of Tom’s approach is his emphasis on testing rather than guessing.
Bellingham Functional Medicine operates online, which means clients can arrange virtual appointments, receive recommendations for laboratory work when appropriate, and order recommended supplements from home. Before an appointment, clients complete a detailed online questionnaire covering their health history, current symptoms, nutrition, lifestyle, and individual concerns.
Tom’s initial consultation lasts one full hour. During the virtual visit, he reviews the questionnaire, asks additional questions, and considers the broader ecosystem of the individual’s health rather than looking at one symptom in isolation.
When the history and symptoms suggest that testing could provide useful information, Tom may recommend laboratory work to explore possible nutrient deficiencies, nutrient excesses, metabolic imbalances, or other factors that may be affecting health. After the appointment, clients receive an email summary containing recommendations and resources. Those who complete laboratory testing can then schedule a follow-up visit to review the results.
Depending on the individual and the practitioner’s judgment, nutritional evaluation may involve areas such as:
Complete blood count
Iron and ferritin
Vitamin B12 and folate
Vitamin D
Electrolytes
Blood-glucose markers
Kidney and liver function
Dietary intake and food variety
Digestive health
Possible microbiome-related factors
Symptoms associated with undernutrition or nutrient imbalance
Not every person needs every test. Testing should be based on health history, symptoms, diet, medication use, existing medical information, and the likelihood that a result will change the care plan.
Laboratory work can provide valuable direction, but it should not be presented as capable of explaining every symptom or diagnosing every condition. Results should be interpreted within the person’s complete medical and nutritional picture.
Book a Virtual Appointment With Tom Malterre
Are you using a GLP-1 medication and concerned about fatigue, reduced food intake, digestive changes, nutrient status, muscle loss, or whether laboratory testing might be appropriate?
You can work with Tom Malterre virtually from home. Complete the detailed questionnaire before your appointment so he can use the consultation to explore your history, symptoms, nutrition, lifestyle, and individual health needs.
Tom’s functional nutrition services can complement, but do not replace, the care of the physician or qualified healthcare professional prescribing and monitoring your medication.
Do GLP-1 Medications Directly Cause Malabsorption?
This distinction matters.
GLP-1 medications delay stomach emptying, increase fullness, reduce appetite, and can change the amount and types of food a person wants to eat. Some people also experience gastrointestinal side effects that make eating and drinking more difficult.
These effects can contribute to inadequate nutrient intake. However, that is not the same as proving that GLP-1 medications cause generalized malabsorption in every user.
A 2025 retrospective observational study examined nutritional diagnoses among more than 460,000 adults after starting GLP-1 receptor agonist treatment. Nutritional deficiencies were documented in 12.7% within six months and 22.4% within one year. The study identified an important association, but because it relied on retrospective medical data, it could not prove that the medication directly caused every deficiency.
The most accurate message is:
GLP-1 therapy may create conditions in which inadequate nutrition becomes more likely—especially when appetite is greatly reduced, gastrointestinal symptoms continue, food variety narrows, or weight is being lost rapidly.
Weight Loss Is Not the Same as Fat Loss
When body weight decreases, some of the loss usually comes from fat and some from fat-free tissue.
Lean mass includes muscle, but it also includes water, organs, connective tissue, and other non-fat components. A reduction in lean mass on a body-composition scan does not automatically mean that the same amount of functional skeletal muscle has been lost.
However, muscle protection still matters.
In a body-composition substudy of the SURMOUNT-1 tirzepatide trial, approximately 75% of the weight lost came from fat mass and 25% from lean mass. Participants experienced substantial reductions in fat, but the lean-mass change reinforces the need to monitor protein intake, strength, function, and exercise during significant weight loss.
More recent research also suggests that clinically significant muscle deterioration is not inevitable. The 2026 SEMALEAN study reported substantial fat reduction during semaglutide treatment alongside preserved lean mass and improved measures of muscle function.
This is why the scale cannot be the only measurement that matters.
We should also ask:
Are you maintaining leg strength?
Can you get out of a chair confidently?
Is your balance improving or declining?
Can you walk farther without fatigue?
Are you recovering from exercise?
Can you carry groceries, climb stairs, hike, travel, or play with your grandchildren?
Are you maintaining independence?
Those are functional-health outcomes.
The Health and Exercise Prescriptions® GLP-1 Support Plan
A 2025 multidisciplinary advisory on nutritional priorities during GLP-1 therapy recommended baseline assessment, nutrient-dense foods, gastrointestinal symptom management, adequate protein, strength training, sleep support, and ongoing evaluation of strength, function, and body composition.
Here is how I translate that science into a practical whole-body prescription.
1. Make Smaller Meals More Nutrient-Dense
When total food volume decreases, every meal needs to perform more nutritional work.
Build meals around:
A quality protein source
Vegetables or fruit
A tolerable source of fiber
Healthy fats
Enough total energy to support daily function and recovery
The goal is not to force large meals through nausea or early fullness. The goal is to identify foods that provide meaningful nutrition in portions the person can tolerate.
Protein needs should be individualized according to age, body size, activity level, rate of weight loss, kidney function, medical conditions, and dietary preferences.
2. Strength Train to Preserve Function
Protein alone cannot replace the physical signal created by resistance exercise.
The body needs a reason to preserve strength. Structured resistance training tells muscle tissue that it is still required for walking, lifting, carrying, climbing, balancing, and living independently.
For someone who is deconditioned, post-rehabilitation, managing pain, or returning after a long break, an appropriate starting plan might include:
Supported chair squats
Resistance-band pulling
Wall or elevated pressing
Step-ups
Loaded carries
Balance training
Progressive walking
Joint-specific mobility
The correct dose is not the hardest workout a person can survive. It is the level of exercise that is safe enough to repeat and progressive enough to produce adaptation.
3. Introduce Fiber Gradually
Fiber supports bowel health, blood-sugar regulation, cholesterol management, and the gut microbiome. But adding a large amount too quickly while digestion is already slower can increase bloating, pressure, constipation, or discomfort.
Increase fiber gradually and pair it with adequate fluid. Oats, beans, lentils, berries, vegetables, chia seeds, ground flax, psyllium, and resistant starches can all be useful, but the right type and amount will vary.
Fiber should support the digestive system, not overwhelm it.
4. Protect Hydration
Some people eat less and unintentionally begin drinking less. Nausea, vomiting, diarrhea, constipation, exercise, heat exposure, and other medications can further change fluid and electrolyte needs.
Watch for persistent dizziness, unusual weakness, severe headaches, very dark urine, fainting, confusion, rapid heart rate, or an inability to keep fluids down. These symptoms require appropriate medical attention, not simply another supplement.
People with kidney disease, heart disease, uncontrolled blood pressure, or medications affecting potassium or sodium should speak with a healthcare professional before using electrolyte products.
5. Monitor Function, Not Just Pounds
Tracking body weight can be useful, but it is incomplete.
A more meaningful monitoring plan may include:
Grip strength
Chair-stand ability
Walking endurance
Balance
Exercise tolerance
Recovery between sessions
Waist circumference
Body composition when appropriate
Energy levels
Protein and food intake
Relevant laboratory markers
The purpose of weight loss should be to improve health—not to trade body weight for weakness.
Where Supplements May Fit
Supplements should support the foundation, not replace it.
A multivitamin cannot compensate for chronically inadequate protein. Amino acids cannot replace resistance training. Electrolytes cannot correct persistent vomiting or a serious medical problem. A probiotic cannot compensate for a diet with no fiber or food variety.
Thoughtfully selected supplements may still help address identified gaps or provide practical support when appetite and meal volume are limited.
Options for foundational nutrition, amino acids, digestive support, hydration, metabolic health, and recovery are available through the:
Review supplements with your physician, pharmacist, prescribing clinician, registered dietitian, or qualified healthcare provider—particularly when taking diabetes medication, blood-pressure medication, anticoagulants, diuretics, or other prescriptions.
Two Complementary Forms of Support
Bellingham Functional Medicine and Health and Exercise Prescriptions® address different parts of the GLP-1 support picture.
Bellingham Functional Medicine offers virtual functional nutrition consultations, detailed health-history review, recommendations for laboratory testing when indicated, nutrition and lifestyle guidance, and individualized nutrient support.
Health and Exercise Prescriptions® helps clients build the physical side of the prescription through medical exercise, progressive strength training, mobility, balance, cardiovascular conditioning, recovery education, and sustainable health planning.
Neither service replaces the physician or healthcare professional prescribing and monitoring GLP-1 medication.
The strongest model is coordinated care:
Medical oversight + nutritional evaluation + appropriate testing + safe exercise + recovery support.
The Real Goal: Lose Weight Without Losing Your Strength
The purpose of GLP-1 treatment should not be to make someone smaller at any cost.
The purpose should be to improve health while protecting the tissues, abilities, and daily functions that make life possible. That means preserving enough strength to work, hike, travel, carry groceries, get off the floor, play with grandchildren, recover after illness, and remain independent.
GLP-1 medications may reduce the biological pressure to overeat. That can create a powerful opening for change.
But that opening still needs to be filled with nourishment, movement, recovery, testing when appropriate, and a sustainable structure.
Your body is not merely losing weight.
It is adapting to a new metabolic environment.
Give it a complete prescription.
Work With Health and Exercise Prescriptions®
Are you using a GLP-1 medication, returning to exercise after significant weight loss, or concerned about losing muscle and physical capacity?
Health and Exercise Prescriptions® provides individualized exercise and wellness planning for adults who need a safe, structured approach to strength, mobility, cardiovascular conditioning, balance, and post-rehabilitation fitness.
Related Health and Exercise Prescriptions® Articles
Scientific References
Mozaffarian D, et al. Nutritional Priorities to Support GLP-1 Therapy for Obesity. 2025.
Butsch WS, et al. Nutritional Deficiencies and Muscle Loss in Adults With Type 2 Diabetes Using GLP-1 Receptor Agonists. 2025.
Look M, et al. Body-Composition Changes During Weight Reduction With Tirzepatide in the SURMOUNT-1 Study. 2025.
Alissou M, et al. Impact of Semaglutide on Fat Mass, Lean Mass, and Muscle Function: The SEMALEAN Study. 2026.
Lincoff AM, et al. Semaglutide and Cardiovascular Outcomes in Obesity Without Diabetes. New England Journal of Medicine. 2023.
Medical and Exercise Disclaimer
This content is for educational purposes only and does not constitute medical, nutritional, supplement, diagnostic, or rehabilitation advice. Consult your physician, prescribing clinician, pharmacist, registered dietitian, or another qualified healthcare provider before starting or changing medication, supplementation, diet, laboratory testing, or exercise—especially if you have pain, injuries, cardiovascular disease, diabetes, kidney disease, gastrointestinal conditions, metabolic disorders, or other medical concerns.
Do not stop, reduce, increase, or otherwise alter a GLP-1 medication without guidance from the prescribing healthcare professional. Stop exercising and seek appropriate medical attention if you experience sharp pain, chest discomfort, fainting, severe dizziness, unusual shortness of breath, confusion, persistent vomiting, or other concerning symptoms.
Author Bio
Jaime Hernandez is a certified health and wellness professional with 25 years of expertise in medical exercise, personal training, therapeutic bodywork, massage, and holistic fitness. He is the founder and Executive Coach of Health and Exercise Prescriptions® in Bellingham, WA, where he develops personalized health and wellness plans designed to help individuals improve strength, mobility, and overall well-being across all stages of life.
Jaime holds certifications as a Medical Exercise Specialist, Licensed Massage Therapist #MA60804408, and trainer in Yoga, Pilates, and Craniosacral Therapy, combining multiple modalities to support post-rehabilitation recovery, preventive health, and functional movement optimization. His approach blends science-based exercise prescription with therapeutic practice to help clients prevent disease, manage chronic conditions, and achieve their health goals.
Health and Exercise Prescriptions®
Thank you for your time and energy...Be well.
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