From the Guidelines
A comprehensive medical weight loss algorithm for obese patients should begin with a thorough assessment including BMI calculation, medical history, and screening for secondary causes of obesity, followed by lifestyle modifications as the foundation, and then consider pharmacotherapy or bariatric surgery as needed, as recommended by the 2013 AHA/ACC/TOS guideline for the management of overweight and obesity in adults 1.
Key Components of the Algorithm
- Start with lifestyle modifications: prescribe a calorie deficit of 500-1000 calories/day, recommend 150-300 minutes of weekly physical activity, and implement behavioral therapy, as supported by the National Heart, Lung, and Blood Institute's report on weight loss interventions 1.
- For patients with BMI ≥30 kg/m² or ≥27 kg/m² with obesity-related comorbidities who don't achieve adequate weight loss after 3-6 months, consider pharmacotherapy, such as semaglutide, tirzepatide, or phentermine-topiramate, as recommended by the American College of Physicians' clinical practice guideline on pharmacologic and surgical management of obesity in primary care 1.
- Monitor patients monthly initially, then quarterly, assessing weight loss, side effects, and comorbidity improvements, and adjust the treatment plan as needed.
- For patients with BMI ≥40 kg/m² or ≥35 kg/m² with comorbidities who don't respond to medical therapy, consider bariatric surgery referral, as recommended by the 2013 AHA/ACC/TOS guideline 1.
Rationale for the Algorithm
The algorithm is based on the evidence that lifestyle modifications, including diet and exercise, are the foundation of weight loss treatment, and that pharmacotherapy and bariatric surgery can be effective adjuncts for patients who do not achieve adequate weight loss with lifestyle modifications alone, as supported by the American College of Physicians' clinical practice guideline on pharmacologic and surgical management of obesity in primary care 1.
Benefits and Risks of the Algorithm
The algorithm has the potential to improve weight loss outcomes, reduce the risk of obesity-related comorbidities, and improve quality of life for obese patients, as supported by the 2013 AHA/ACC/TOS guideline 1. However, it also carries potential risks, such as side effects from pharmacotherapy and complications from bariatric surgery, which must be carefully weighed and monitored by healthcare providers.
From the FDA Drug Label
Phentermine Hydrochloride, USP 15 mg and 30 mg is indicated as a short-term (a few weeks) adjunct in a regimen of weight reduction based on exercise, behavioral modification and caloric restriction in the management of exogenous obesity for patients with an initial body mass index greater than or equal to 30 kg/m 2, or greater than or equal to 27 kg/m 2 in the presence of other risk factors (e.g., controlled hypertension, diabetes, hyperlipidemia).
The algorithm for medical weight loss options for obese patients using phentermine is as follows:
- Indications: Phentermine is indicated for patients with a BMI ≥ 30 kg/m² or ≥ 27 kg/m² with other risk factors.
- Dosage: The usual adult dose is 15-30 mg at approximately 2 hours after breakfast for appetite control.
- Contraindications: Phentermine is contraindicated in patients with a history of cardiovascular disease, hyperthyroidism, glaucoma, agitated states, history of drug abuse, pregnancy, nursing, and known hypersensitivity to sympathomimetic amines.
- Warnings and Precautions: Phentermine should be used with caution in patients with renal impairment, and the recommended maximum dosage is 15 mg daily for patients with severe renal impairments.
- Monitoring: Patients should be monitored for potential adverse reactions, including primary pulmonary hypertension, serious valvular heart disease, and increased blood pressure.
From the Research
Medical Weight Loss Options
To develop an algorithm for medical weight loss options, several factors must be considered, including dietary approaches, physical activity, and behavioral modifications.
- The optimal dietary approach should be safe, efficacious, healthy, and nutritionally adequate, as well as culturally acceptable and economically affordable 3.
- A reduced-calorie diet, increased physical activity, and behavior therapy are key components of intensive lifestyle interventions for weight loss, with a minimum of 6 months of high-intensity intervention recommended 4.
- Seven FDA-approved anti-obesity medications are available, including phentermine, orlistat, and liraglutide, which should be prescribed with the intention of long-term use 5.
Lifestyle Modifications
Lifestyle modifications are first-line therapy for patients with overweight or obesity, and the most effective weight loss intervention includes:
- A moderately reduced-calorie diet
- Increased physical activity
- The use of behavior strategies to facilitate adherence 6
- Adults should engage in at least 150 to 300 min/week of moderate-intensity or 75 to 150 min/week of vigorous-intensity aerobic physical activity for substantial health benefits 6
Physical Activity
Physical activity is a key component of weight loss interventions, with benefits including:
- Additive effects to dietary restriction alone
- Prevention of weight regain and maintenance of significant weight loss
- Contribution to weight loss in patients who have undergone bariatric surgery 7
- Interindividual variability in weight loss resulting from physical activity, with both biological and behavioral factors contributing to this variability 7