Insights on Metabolism & Metabolic Rates

Why Weight Loss Can Stall — Even When You’re Doing Everything Right

Many people eat less, exercise more, and still struggle to lose weight. This is not always due to lack of effort or “willpower.” In some cases, the problem is something called metabolic suppression, also known as a “slow metabolism.” ¹ ²

What Is Metabolic Suppression?

Metabolic suppression happens when your body starts burning fewer calories than expected, even at rest. This can occur after long periods of dieting, eating too few calories, or losing weight repeatedly (yo-yo dieting).³

Normally, when we lose weight, our bodies burn fewer calories simply because we are smaller. But with metabolic suppression, the body burns even fewer calories than expected, making weight loss — or even maintaining weight — extremely difficult.³ ⁴

Why Does This Happen?

Your body is built to survive. When it senses you’re not getting enough food, it tries to protect you by conserving energy. It does this by:⁴ ⁵

• Lowering your resting metabolic rate (RMR)
• Reducing hormones like thyroid hormone (T3) and leptin⁵ ⁶
• Increasing hunger hormones like ghrelin
• Breaking down muscle instead of fat if you don’t get enough protein or don’t do strength training
• Reducing movement and energy — you may feel cold, tired, or unmotivated⁷

Common Causes of a Slower Metabolism

• Very low-calorie diets or skipping meals
• Crash diets or rapid weight loss
• Loss of muscle mass (no resistance training, low protein)
• Poor sleep or high stress
• Repeated weight loss and regain (yo-yo dieting)
• Hormonal changes (thyroid disease, menopause, low leptin)
• Long-term obesity — especially BMI ≥ 30, where calorie calculators often overestimate your metabolic rate⁸

Signs You May Have a Suppressed Metabolism

• You’re eating less, but weight loss has stopped
• You gain weight easily, even with small meals
• You feel cold, tired, or low energy
• You feel constantly hungry or have strong cravings
• Hair thinning, dry skin, or irregular periods
• Calorie-tracking apps say you should be losing weight — but you’re not

How Do You Know for Sure?

Most people use online calorie calculators — but these formulas can be wrong by 200–500 calories per day, especially if your BMI is 30 or more.⁸

At Thames Diagnostics, we measure your actual metabolic rate using indirect calorimetry — not just formulas — and we see metabolic suppression in about 10% of referred patients.

Why Metabolic Rate Testing Matters 

✔ Shows if your metabolism is slower than expected

✔ Helps doctors and dietitians choose the right calorie target

✔ Helps prevent under-eating that can make metabolism worse

✔ Tracks metabolic recovery after weight loss

✔ Replaces guesswork with real numbers⁹ ¹⁰

Can You Fix a Suppressed Metabolism? Yes — With the Right Plan

Ways to help restore metabolic function include:

• Work with your health care team (e.g. dietitian, family doctor/NP,  fitness professional)
• Eat enough calories — don’t starve yourself
• Aim for 1.2–1.6 g/kg of protein per day¹⁶
• Avoid long-term crash dieting
• Take short “maintenance breaks” instead of dieting constantly¹²
• Do strength training to rebuild muscle
• Get 7–8 hours of sleep and manage stress
• Treat medical issues if present (thyroid problems, anemia, sleep apnea)
• Track recovery using indirect calorimetry¹³ ¹⁴

Why This Matters Even More for BMI ≥ 30

If your BMI is 30 or more:

• Most calorie calculators overestimate how many calories you burn⁸
• Diet plans might not work — even when followed perfectly
• You could be unfairly judged as “noncompliant” when the real issue is your metabolism, not your effort

Final Takeaway

• Struggling to lose weight does not mean you’re not trying hard enough
• Metabolic suppression is real, measurable, and scientifically proven
• If BMI ≥ 30, most formulas overestimate metabolic rate
• Indirect calorimetry (metabolic rate testing) provides real answers
• With accurate data, weight loss becomes safer, more realistic, and more effective

References

Rosenbaum M, Leibel RL. Adaptive thermogenesis in humans. StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023.
https://www.ncbi.nlm.nih.gov/books/NBK560523/

1. Martins C, Gower BA, Hunter GR. Metabolic adaptation is not a major barrier to weight loss maintenance. Am J Clin Nutr. 2020;112(3):558–565.
   https://doi.org/10.1093/ajcn/nqaa123
2. Fothergill E, Guo J, Howard L, et al. Persistent metabolic adaptation 6 years after “The Biggest Loser” competition. Obesity (Silver Spring). 2016;24(8):1612–1619.
   https://pubmed.ncbi.nlm.nih.gov/27136388/
3. Heinitz S, Grundling M, Stengel A. Metabolic adaptation following weight loss: a systematic review. Metabolism. 2020;104:154–163.
   https://doi.org/10.1016/j.metabol.2019.154163
4. Yu H, Xia F, Lam SK, et al. Thyroid hormones and leptin in obesity and metabolic syndrome. Eur Thyroid J.2019;8(3):147–159.
   https://doi.org/10.1159/000500080
5. Rosenbaum M, Hirsch J, Gallagher DA, Leibel RL. Long-term persistence of adaptive thermogenesis after weight loss. Am J Clin Nutr. 2008;88(4):906–912.
   https://pubmed.ncbi.nlm.nih.gov/18842775/
6. Martin A, et al. Tissue-specific metabolic adaptation during weight loss and maintenance. Int J Obes.2022;46(1):35–44.
   https://doi.org/10.1038/s41366-021-00979-2
7. Frankenfield DC, Roth-Yousey L, Compher C. Comparative analysis of predictive equations for resting metabolic rate in adults. J Am Diet Assoc. 2005;105(5):775–789.
   https://pubmed.ncbi.nlm.nih.gov/15883556/
8. Delsoglio M, Achamrah N, Berger MM, Pichard C. Indirect calorimetry in clinical practice. J Clin Med.2019;8(9):1387.
   https://doi.org/10.3390/jcm8091387
9. Achamrah N, et al. Can indirect calorimetry help tailor metabolic needs after weight changes? Clin Nutr.2021;40(1):4–10.
   https://doi.org/10.1016/j.clnu.2020.07.007
10. Levine JA. Nonexercise activity thermogenesis (NEAT): environment and biology. Science.2005;307(5709):584–586.
    https://doi.org/10.1126/science.1104268
11. Dulloo AG, Montani JP, Schutz Y. Adaptive thermogenesis in resistance to obesity therapies. Int J Obes.2021;45(9):1977–1988.
    https://doi.org/10.1038/s41366-021-00878-6
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    https://doi.org/10.1093/ajcn/nqaa123
13. Leidy HJ, Clifton PM, Astrup A, et al. The role of protein in weight loss and maintenance. Am J Clin Nutr.2015;101(6):1320–1329.
    https://doi.org/10.3945/ajcn.114.084038

A practical, science-backed guide for real people working to improve their metabolism

Your resting metabolic rate (RMR) is the number of calories your body burns at rest — to breathe, circulate blood, maintain temperature, repair tissues, and run your brain and organs. A healthy metabolism makes weight loss and maintenance easier, safer, and more predictable.

Many people believe they have a “slow metabolism,” but research shows:

• Some do, and it can be measured (not guessed) with indirect calorimetry. [1] 
• Others are unintentionally under-fueling or losing muscle, which slows RMR. [2–4]
• Common formulas often overestimate RMR in adults with BMI ≥30, so measured data prevents mis-targeting calories. [5]

Your metabolism is not fixed — and you can improve it safely. Below are the 10 most effective, science-supported strategies, ranked by metabolic impact.

1) Build and Maintain Lean Muscle

Effectiveness: highest | Practicality: high

Muscle is metabolically active tissue. More muscle = more calories burned at rest. Resistance training increases or preserves lean mass and helps maintain RMR during weight loss. [2–4,6–8]

Do: strength train 2–3×/week; progress load/reps/tempo over time; train major muscle groups.

2) Protect Your Existing Muscle (during weight loss)

Effectiveness: very high | Practicality: high

Muscle loss = metabolic slowdown. During calorie deficits, combine adequate protein and resistance training to minimize lean-mass loss and preserve RMR. [2–4,6–9]

3) Support Thyroid & Hormonal Health

Effectiveness: very high (when impaired) | Practicality: moderate

Thyroid hormones (T3/T4) help set basal metabolic rate; low thyroid function reduces RMR. Leptin and other energy-regulating hormones drop with chronic energy restriction/weight loss and contribute to metabolic adaptation (lower energy expenditure than predicted). [3,4,10–12]

Do: avoid crash dieting, sleep well, manage stress, eat adequately; seek medical assessment if hypothyroid symptoms exist.

4) Avoid Crash Dieting (Fuel Your Body)

Effectiveness: very high | Practicality: moderate

Severe restriction accelerates muscle loss and exaggerates metabolic adaptation, lowering RMR beyond what weight loss alone predicts and increasing risk of weight regain. [3,4,11–13]

Do: use moderate deficits; consider planned maintenance phases; pair with protein + resistance training.

5) Increase NEAT (Non-Exercise Activity Thermogenesis)

Effectiveness: very high (especially if sedentary) | Practicality: very high NEAT — all movement outside the gym — can vary by hundreds to >1000 kcal/day across people and strongly influences weight trajectory. [14]

Do: aim for 7–10k steps/day (or +2k from baseline); stand/walk breaks; stairs; “movement snacks.”

6) Aerobic Exercise (Used Strategically)

Effectiveness: high | Practicality: high

Consistent moderate cardio improves insulin sensitivity, mitochondrial function, fat oxidation, and total daily energy expenditure; pairing with resistance training best preserves RMR. [6–8,15]

Do: 150–300 min/week moderate or 75–150 min/week vigorous. Walking is an excellent starting point. Medical clearance advised for high-risk individuals.

7) Optimize Protein Intake

Effectiveness: high | Practicality: high

Protein has the highest thermic effect of food, improves satiety, and protects lean mass during weight loss, supporting RMR. Target ~1.2–1.6 g/kg/day distributed across meals. [7–9,16]

Do: include protein every meal; mix whole-food sources; use shakes if needed; pair with resistance training.

8) Combine Strength + Cardio (Best Synergy)

Effectiveness: high | Practicality: highPrograms that combine resistance + aerobic outperform either alone for fat loss, insulin sensitivity, metabolic flexibility, and long-term weight control — while protecting RMR via lean-mass preservation. [6–8,15]

Do: strength 2–3×/week plus cardio 2–4×/week, progressed gradually.

9) Improve Sleep & Circadian Rhythm

Effectiveness: moderate-to-high | Practicality: high

Short or poor-quality sleep disrupts appetite hormones (ghrelin↑, leptin↓), reduces insulin sensitivity, lowers daily activity, and can reduce RMR. Improving sleep (7–9 h; consistent timing; light/caffeine/alcohol hygiene) supports metabolic health and weight control. [17–19]

Do: wind-down routine; cool/dark room; morning light exposure; finish eating 2–3 h before bed.

10) Manage Stress & Support Recovery

Effectiveness: moderate-to-high (strong long-term impact) | Practicality: high

Chronic stress (cortisol↑) increases appetite/cravings, impairs sleep, reduces NEAT, and hampers muscle recovery — indirectly suppressing metabolism and weight-loss adherence. [18–21]

Do: daily 10-minute decompression (breathwork, walk, mindfulness, stretching, journaling); prioritize recovery days; limit late caffeine and excess alcohol.

Why Indirect Calorimetry Helps

Because metabolism varies widely — and prediction formulas can be inaccurate in higher BMI — measuring your actual RMR prevents under- or over-fueling, protects lean mass during weight loss, and helps detect metabolic adaptation. [1,5,11,12]

IC turns guesswork into reliable data, enabling safer calorie targets and better long-term outcomes.

Medical Safety Notes

• Discuss new exercise programs (especially resistance or vigorous aerobic training) with a clinician if you have chronic conditions, high BMI, diabetes, cardiac disease, or long inactivity.
• Seek medical evaluation for suspected thyroid disease, amenorrhea, severe fatigue, or unexplained weight change.
• Individuals with kidney disease should review higher-protein targets with their clinician.

Final Takeaway

You don’t need extreme diets or exhausting workouts. The most powerful metabolic plan is balanced, consistent, and personalized:

• Lift weights, move daily, prioritize protein, fuel (don’t starve), sleep well, manage stress, and — when available — use indirect calorimetry to personalize targets. [1–5,7–9,11–19]

Your metabolism is adaptable — and with science-based habits, you can improve it safely and sustainably.

References (hyperlinked)

1. Delsoglio M, Achamrah N, Berger MM, Pichard C. Indirect calorimetry in clinical practice. J Clin

Med.2019;8(9):1387. https://doi.org/10.3390/jcm8091387

2. Stiegler P, Cunliffe A. The role of diet and exercise for the maintenance of fat-free mass and resting

metabolic rate during weight loss. Sports Med. 2006;36(3):239–262.

https://doi.org/10.2165/00007256-200636030-00005

3. Fothergill E, Guo J, Howard L, et al. Persistent metabolic adaptation 6 years after “The Biggest Loser”

competition. Obesity (Silver Spring). 2016;24(8):1612–1619.

https://pubmed.ncbi.nlm.nih.gov/27136388/

4. Dulloo AG, Montani JP, Schutz Y. Adaptive thermogenesis in resistance to obesity therapies. Int J Obes

(Lond).2021;45(9):1977–1988. https://doi.org/10.1038/s41366-021-00878-6

5. Frankenfield DC, Roth-Yousey L, Compher C. Comparison of predictive equations for resting metabolic

rate in healthy nonobese and obese adults: a systematic review. J Am Diet Assoc.

2005;105(5):775–789. https://pubmed.ncbi.nlm.nih.gov/15883556/

6. Willis LH, Slentz CA, Bateman LA, et al. Effects of aerobic and/or resistance training on body mass and

fat mass in overweight or obese adults. J Appl Physiol. 2012;113(12):1831–1837.

https://doi.org/10.1152/japplphysiol.01370.2011

7. Leidy HJ, Clifton PM, Astrup A, et al. The role of protein in weight loss and maintenance. Am J Clin

Nutr.2015;101(6):1320–1329. https://doi.org/10.3945/ajcn.114.084038

8. Cermak NM, Res PT, de Groot LCPGM, Saris WHM, van Loon LJC. Protein supplementation augments

the adaptive response of skeletal muscle to resistance-type exercise training. Am J Clin Nutr.

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9. Helms ER, Zinn C, Rowlands DS, Brown SR. A systematic review of dietary protein during caloric

restriction in resistance-trained lean athletes: a case for higher intakes. Int J Sport Nutr Exerc Metab.

2014;24(2):127–138. https://doi.org/10.1123/ijsnem.2013-0054

10. Rosenbaum M, Hirsch J, Gallagher DA, Leibel RL. Long-term persistence of adaptive thermogenesis in

subjects who have maintained a reduced body weight. Am J Clin Nutr. 2008;88(4):906–912.

https://pubmed.ncbi.nlm.nih.gov/18842775/

11. Martins C, Gower BA, Hunter GR. Metabolic adaptation is not a major barrier to weight-loss

maintenance. Am J Clin Nutr. 2020;112(3):558–565. https://doi.org/10.1093/ajcn/nqaa123

12. Müller MJ, Bosy-Westphal A. Adaptive thermogenesis with weight loss in humans. Obesity (Silver

Spring).2013;21(2):218–228. https://doi.org/10.1002/oby.20027

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better for metabolic health? Br J Nutr. 2020;124(10):1121–1132.

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Science.2005;307(5709):584–586. https://doi.org/10.1126/science.110426815. Ross R, Goodpaster BH, Koch LG, et al. Precision exercise medicine: understanding exercise

response variability. Br J Sports Med. 2019;53(18):1141–1153.

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controlled trials. Am J Clin Nutr. 2012;96(6):1281–1298. https://doi.org/10.3945/ajcn.112.044321

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men is associated with decreased leptin and increased ghrelin. Ann Intern Med. 2004;141(11):846–850.

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stress. Expert Rev Endocrinol Metab. 2006;1(6):783–792. https://doi.org/10.1586/17446651.1.6.783