Obesity diagnosis and treatment algorithm

A new algorithm that can be used by health care professionals in the evaluation and treatment of obesity is presented.

Data source and selection: After a MEDLINE search, five accepted obesity algorithms were evaluated. 
Results: A new algorithm that provides guidelines for the diagnosis and treatment of obesity, including the indications for pharmaceutical and surgical treatment. 
Conclusions: This algorithm can assist in planning individual patient care and in establishing the treatment requirements for obesity in British Columbia.

When a literature search revealed the absence of a thorough and useful algorithm on obesity diagnosis and treatment, the authors created their own, and present it here.


Obesity refers to an excess of total body fat. Obesity, particularly excess abdominal adipose tissue, increases the risk of the development of numerous co-morbid conditions including atherosclerosis, type II diabetes mellitus, hypertension, hyperlipidemia, and many other life-threatening and costly disorders. However, despite the worldwide prevalence of obesity, there is no internationally accepted algorithm for its treatment. The lack of a common algorithm for the treatment of obesity leads to individualized therapy that may be based more upon the particular opinions of a physician, clinician, or obesity clinic, than on evidence. Using the major algorithms in the literature as a template, we derived a comprehensive obesity algorithm for British Columbia that describes a suggested obesity diagnosis and treatment protocol.


A MEDLINE search was conducted into obesity algorithms; the five that were found were assessed on the following criteria: whether they included discussions of treatment, diagnosis, risk factors, diet, exercise, behavioral treatment, pharmaceutical treatment, and surgery.

Based on these algorithms and data from the literature, a new, more comprehensive algorithm was developed.

Results of the literature search

The MEDLINE literature search revealed the following obesity algorithms:

• The Scottish Intercollegiate Guidelines Network (SIGN) was designed to identify the extent of the obesity epidemic in Scotland.[1] It emphasizes that individuals should be responsible for identifying obesity as a problem and seek treatment from a general practitioner. However, these guidelines lack specificity regarding follow-up procedures and maintenance of weight loss.

• The Swedish Obesity Study (SOS) is an ongoing intervention trial with the intent of recruiting 7,000 to 10,000 subjects.[2] The primary purpose of the study is to compare conventional treatments of obesity versus surgery.

• The National Institute of Health in the United States (NIH) released the first American guidelines on the identification, evaluation, and treatment of adult obesity and co-morbidities in September 1998.[3] Conservative methods of achieving weight loss are emphasized over more aggressive methods such as surgery. This algorithm does not address the issues of medical conditions or medications that predispose to weight gain.

• “Shape Up America” is the United States guideline for the treatment of obesity.[4] The guideline is written for the general practitioner as a tool to help diagnose overweight and obese patients and to help provide treatment options for them. The information provided is very general. Because prescribed guidance and support protocols are minimal, the patient takes on the majority of responsibility for his or her weight loss.

• In 1998, the American Association of Clinical Endocrinologists published a paper on the prevention, diagnosis, and treatment of obesity.[5] Behavior modification is emphasized as the key component to a weight-loss program provided by a number of specialists, but led by one physician.

Diagnosis and treatment algorithm

Our obesity algorithm is presented in the Figure. Obesity is known to be a significant risk factor for various diseases.[6,7] The clinical measurement most commonly used to determine the degree of obesity is the body mass index (BMI).[8] BMI is computed by dividing the weight of the patient in kilograms by the square of the patient’s height in metres, thereby normalizing weight by height. Importantly, BMI does not measure how much of the weight is due to fatty tissue. The clinician, therefore, must examine the patient to determine that a high BMI is not due to, for example, excess muscle or fluid. BMI reliably estimates the risk for the development of diseases caused by obesity.[9] For this reason, it appears as the first decision point in our algorithm. The algorithm uses the three BMI intervals that correspond with the generally accepted values for normal weight, overweight, and obesity.[8] The decision to investigate or treat is then revised based on other risk factors for morbidity and mortality.

A BMI of 20 to 24.9 is considered normal, so no action is taken unless the waist circumference is above normal[10] (i.e., greater than 88 cm in women and greater than 102 cm in men). If the BMI is between 25 and 29.9 and there are two or more risk factors (hypertension, diabetes, and dyslipidemia), further action should be taken. If their waist circumference is elevated, patients with a BMI of 25 to 29.9 may require treatment even if they have no risk factors.[11] An elevated waist circumference is an independent risk factor for type II diabetes, dyslipidemia, hypertension, and cardiovascular disease.[12-15]

If the BMI is between 25 and 29.9 with no risk factors and a normal waist circumference, the practitioner must determine if there has been a history of a BMI greater than or equal to 30. If the weight gain is recent the patient is more likely to respond to general guidelines on diet, exercise, and behavior management. If the problem is long-standing, treatment recommendations depend on the degree of motivation for weight loss. Even if the BMI is greater than 30, motivation must be considered when making treatment decisions.

If the patient is clearly not ready for weight loss, general counseling should be given with the goal of weight maintenance. Co-morbid disease, like hypertension or hyperlipidemia, must be treated, even if there is no motivation to lose weight. If the patient is motivated to lose weight, a team that may consist of a physician, dietitian, physiotherapist, and behavior therapist work with the patient to construct and carry out a plan for weight loss and risk factor management.

The first goal in most cases is a 10% weight loss from baseline over 6 months, which corresponds to a decrease in BMI of 2 units.[16] If the weight loss goals are achieved in 6 months, further goals should be set. If further weight loss is desired, work with the team continues. If weight loss plateaus and all other causes of weight gain are ruled out, pharmacology may aid in the treatment plan.[17] If medications aid in weight loss over the next 6 months and the goals are achieved, maintenance therapy is initiated and the medication is continued.

If the weight loss goal is not achieved in the initial 6 months, noncompliance and other factors that predispose to weight gain need to be ruled out before pharmacotherapy is added to the treatment plan. Among these causes are the medical conditions outlined in Table 1 and some drug treatments outlined in Table 2. Among the causes of refractoriness to weight loss, undiagnosed or inadequately treated depression, alcohol intake, chronic pain, and medications (including over-the-counter medications such as antihistamines) are the most common treatable causes.

If pharmacotherapy is unsuccessful and the BMI is greater than 40, surgery should be considered.[26] Table 3 shows the criteria for surgical intervention used by the Bariatric Surgical Clinic at St. Paul’s Hospital.[26,27] These criteria are the same as those used internationally, except that our age cut-off is 40 years rather than 50 years. This cut-off improves the outcome and reduces the complication rate of bariatric surgery. Long-term follow-up after surgery is essential.

Maintenance therapy after successful weight loss and for those who were not ready for weight loss is a crucial lifelong process. In most cases, weight loss has been achieved many times, but weight maintenance has been unsuccessful. The first step to maintaining weight loss is the acceptance by the physician and the patient that obesity is usually a chronic condition, like hypertension and asthma. The likelihood of weight maintenance is increased by a periodic weight check with reinforcement and encouragement of the need for permanent dietary and exercise change.


This obesity diagnosis and treatment algorithm can assist the physician in the diagnosis and treatment of obesity and its associated co-morbidities. Even if weight loss is not attempted or achieved, weight maintenance and treatment of diseases due to obesity is indicated. Finally, long-term therapy to promote weight maintenance is necessary because obesity is almost always a chronic condition.

Competing interests

None declared.

Table 1. Medical conditions associated with weight gain

Cushing’s syndrome[18]

Prader-Willi syndrome[18]

Bardet-Biedl syndrome[18]


Chronic fatigue syndrome[20]

Lesion of hypothalamic regions[21]

Viral (AD-36)[22]



Table 2. Medications associated with weight gain[24,25]

Antidepressant drugs 
Trycyclic antidepressant drugs 
• Amitripytine 
• Imipramine 
• Amoxapine 
• Maprotile

To less of an effect 
• Desipramine 
• Nortripyline 
• Trazodone 
• Phelezine 
• Nefazodone 
• Moclobemide 
• Trimipramine 
• Tranylcypromine
• Bupropion

Antipsychotic drugs 
• Clozapine 
• Olanzapine 
• Chlorpromazine 
• Perphenazine 
• Thiothixene 
• Fluphenazine 
• Flupenthixol 
• Trifluoperazine 
• Loxapine 
• Thioridazine 
• Haloperidol 
• Molindone 
• Risperidone 
• Quetiapine 
• Zotepine

Mood stabilizers 
• Lithium

Anticonvulsants/mood stabilizers
• Valproic acid 
• Carbamazepine

Steroid hormones

Corticosteroid derivatives 
• Prednisone 
• Dexamethasone

Ovarian steroid hormone derivatives 
• Oral contraceptive medications (controversial) 
• Megestrol acetate 
• Medroxyprogesterone acetate

Diabetes medications 
• Insulin

Oral hypoglycaemic agents 
• All except metformin

Antineoplastic agents 
• Prednisone 
• Tamoxifin

Cannabinoid derivatives 
• Marijauna 
• Dranabinol 
• Merinol 
• Nabilone

Other agents 
• Flunarizine (migraine prophylaxis) 
• Pizotifen 
• Propranolol 
• Danazol

Table 3. Minimum criteria for bariatric surgery[26,27]

• BMI >40 due to increased body fat

• Between 18 and 40 years of age

• Well informed figabout the alternative treatments, risks, complications, and follow-up of the surgery, as well as other types of obesity surgery

• Motivated and able to comply with follow-up management postoperatively (diet, medications, blood work, clinical visits)

• Adequate support systems in place, including a family physician who agrees to provide follow-up

• Likely to derive functional benefit from weight loss

• No psychosis, major depression, or addictive disorder

• No medical contraindications to surgery


1.  Scottish Intercollegiate Guidelines Network. Obesity in Scotland: Integrating Prevention with Weight Management: A National Clinical Guideline Recommended for use in Scotland by the Scottish Intercollegiate Guidelines Network. Edinburgh: SIGN Publication 8, 1996. Full Text 
2.  Sullivan M, Karlsson J, Sjostrom L, et al. Swedish obese subjects (SOS)—An intervention study of obesity. Baseline evaluation of health and psychosocial functioning in the first 1743 subjects examined. Int J Obes Relat Metab Disord 1993;17:503-512. PubMed Abstract 
3.  National Institutes of Health. Clinical guidelines on the identification, evaluation, and treatment of overweight and obesity in adults—The evidence report. Obes Res 1998;6:51S-209S. PubMed Citation Full Text 
4.  No authors listed. Guidance for Treatment of Adult Obesity. Bethesda, MD: American Obesity Association, 1996. Full Text 
5.  AACE/ACE Obesity Task Force. AACE/ACE position statement on the prevention, diagnosis, and treatment of obesity (1998 revision). Endocr Pract 1998;4:297-330. Full Text 
6.  Tanaka K, Nakanishi T. Obesity as a risk factor for various diseases: Necessity of lifestyle changes for healthy aging. App Hum Sci 1996;15:139-148. PubMed Abstract 
7.  World Health Organization. Obesity Epidemic Puts Millions at Risk from Related Diseases. World Health Organization (WHO) Consultation on Obesity. Geneva, Switzerland. 3–5 June 1997. 
8.  World Health Organization. Measuring Obesity—Classification and Distribution of Anthropometric Data. Report on a WHO Consultation on the Epidemiology of Obesity. Warsaw, Poland. 21–23 October 1987:8-10. 
9.  Kato M, Shimazu M, Morigucki S, et al. Body mass index (BMI) is a reliable index to estimate obesity as a risk factor for deteriorating health. Tokushima J Exp Med 1996;43:1-6. PubMed Abstract 
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13. Chan JM, Rimm EB, Colditz GA, et al. Obesity, fat distribution, and weight gain as risk factors for clinical diabetes in men. Diabetes Care 1994;17:961-969. PubMed Abstract 
14. Paccaud F, Schluter-Fasmeyer V, Wietlisbach V, et al. Dyslipidemia and abdominal obesity: An assessment in three general populations. J Clin Epidemiol 2000;53:393-400. PubMed Abstract 
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18. Kirk LF Jr, Hash RB, Katner HP, et al. Cushing’s disease: Clinical manifestations and diagnostic evaluation. Am Fam Physician 2000;62:1119-1127,1133-1134. PubMed Abstract Full Text 
19. Elliott B. Diagnosing and treating hypothyroidism. Nurse Pract 2000;25:92-94,99-105. PubMed Abstract 
20. Jebb SA, Moore MS. Contribution of a sedentary lifestyle and inactivity to the etiology of overweight and obesity: Current evidence and research issues. Med Sci Sports Exerc 1999;31:S534-S541. PubMed Abstract 
21. Namnoum AB. Obesity: A disease worth treating. Female Patient 1993;18:33-44. 
22. Dhurandhar NV, Israel BA, Kolesar JM, et al. Increased adiposity in animals due to a human virus. Int J Obes Relat Metab Disord 2000;24:989-996. PubMed Abstract 
23. Felitti VJ. Childhood sexual abuse, depression, and family dysfunction in adult obese patients: A case control study. South Med J 1993;86:732-736. PubMed Abstract 
24. Pijl H, Meinders AE. Bodyweight change as an adverse effect of drug treatment. Mechanisms and management. Drug Saf 1996;14:329-342. PubMed Abstract 
25. Chiesi M, Huppertz C, Hofbauer KG. Pharmacotherapy of obesity: Targets and perspectives. Trends Pharmacolog Sci 2001;22:247-254. PubMed Abstract 
26. Guidelines for laparoscopic and open surgical treatment of morbid obesity. American Society for Bariatric Surgery. Society of American Gastrointestinal Endoscopic Surgeons. Obes Surg 2000;10:378-379. PubMed Citation 
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Kathleen M.N. Lee, RDN, Lee M. Jonat, BSc, and C. Laird Birmingham, MD, MHSc, FRCPC, FACP, ABIM

Ms Lee is a clinical dietitian at St. Paul’s Hospital. Mr Jonat is a research student in the Eating Disorders Program at St. Paul’s Hospital. Dr Birmingham is the medical director of the Eating Disorders Program at St. Paul’s Hospital, the British Columbia provincial director for Eating Disorders, a professor of medicine at the University of British Columbia, and the team leader for the Centre for Health Evaluation and Outcome Sciences.

Kathleen M.N. Lee, RDN, Lee M. Jonat, BSc, C. Laird Birmingham, MD, MHSc, FRCPC, FACP, ABIM. Obesity diagnosis and treatment algorithm. BCMJ, Vol. 44, No. 3, April, 2002, Page(s) 126-130 - Clinical Articles.

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