Introduction 1 2 3 4 5 6 6 1 4 6 7 8 9 To date, literature reviews have given conflicting views based on the available data and method of data retrieval. The purpose of this review is to establish, from recent research, if there is a causal link between obesity and the affliction of low back pain. A secondary purpose of this review is to present the concepts of evidence-based practice to aid the chiropractor or osteopath in looking for health-related evidence for their patients who present with obesity. Methods A MEDLINE search, from the National Library of Medicine, was used to ascertain pertinent articles between the years 1990 and 2004. The use of keywords "obesity", "body mass index", "BMI" and "low back pain" was used to obtain relevant studies. The references of papers retrieved were also reviewed, as were key texts and references. 1 Table 1 Steps to asking the answerable question using EBP principles Step 1: Asking an answerable question Step 2: Selecting an evidence resource Step 3: Executing the search strategy Step 4: Examining the evidence summary Step 5: Application of the evidence The first step in this process is "asking an answerable question." In this paper we assume a patient has asked whether being overweight can cause low back pain. Construction of an appropriate answerable question would possibly be "Does an increased BMI cause low back pain?" "Does being overweight create osteoarthritis?" In this way questions can be constructed to allow the practitioner to effectively answer a clinical concern. Once the answerable question has been constructed the next task is to find an adequate resource. Internet access to the U.S. National Library of Medicine's MEDLINE or PUBMED, these database systems are considered by many experts to be the most up to date data source on medically related topics. The next step is to determine keywords to place in the search engine. From the answerable question(s) it can be appreciated that the initial keywords will be "low back pain", "BMI" and "osteoarthritis." This search constitutes the third step. In initiating the search, one should look for the search engines "limits" area. In this area can one designate an age group (ex: 45 to 60 years), date span of the literature search, (ex: 1998 to 2003), and to select either English language or articles in foreign languages. 2 Table 2 Recent evidence: Obesity and low back pain (chronological order) Author, Year (Ref) N BMI LBP Association Melissas, 2003 [14] 50 >40 58% direct Bener, 2003 [10] 802 (26.4 males/ 27.8 females) 56.1% males     73.8% females moderate Tsuritani, 2002 [16] 709 -- 40.3% none Bowerman, 2001 [4] 252 -- 29.2% none Kostova, 2001 [12] 898 -- -- increased risk Bayramoglu, 2001 [15] 25 -- -- direct Mortimer, 2001 [13] 475 30 (43.6%)     31–40 (28.8%)     40+ (1.3%) -- increased risk Han, 1997 [11] 7018 women 5887 men NR --  females increased risk N = number; BMI = body mass index; LBP = low back pain; NR = not reported It is at this time that the clinician is ready for the final step of applying the evidence. In our example clinical data from the experimental literature may or may not indicate that there is a link between overweight and low back pain. Results 2 4 10 13 14 15 4 16 Discussion 17 18 19 Body mass index 2  20 15 20 21 19 20 21 22 3 22 23 4 4 23 Table 3 Clinically relevant differentiation between obesity and overweight Overweight Obesity 2 2 BMI calculation without benefit of BMI charts Body Mass Index (BMI) charts and hand held scales are available for individual clinician use. It is, however, unknown to what degree chiropractors or osteopaths use such tools. The following section is designed to aid the clinician with calculating BMI without benefit of chart or hand held scales. 20 24 4 Table 4 Calculation of BMI 150 × 703 = 105450 divided by 72 inches (6 foot) squared. 105450 divided by 5184 (72 × 72) = 20.3 BMI. Additional research findings 25 12 26 27 26 27 28 Obesity and low back pain-related conditions et al  29 29 et al  30 30 31 et al  32 33 35 9 9 36 5 Table 5 BMI-related risk of osteoarthritis and low back pain If your BMI is then your risk based solely on BMI <25 minimal 25 – <27 minimal 27 – <30 minimal 30 – <35 moderate 35 – <40 moderate >40 moderate to high 14 5 Limitations of obesity as a risk factor for low back pain A significant difficulty in ascertaining cause and effect between obesity and low back pain is undoubtedly the term "low back pain" itself. Low back pain is a symptom not a diagnosis. A specific diagnosis, instead of the generalized form of "low back pain" may help separate out the association between LBP and obesity. Acute Low Back Problems in Adults  6 Table 6 Common diagnoses used to explain back symptoms Annular tear Adult spondylolysis Myofascitis Fibromyalgia Disc syndrome Strain Spondylosis Lumbar disc disease Facet syndrome Degenerative joint disease Sprain Spinal OA Disc derangement/disruption  Dislocation  *Other potential causes of low back pain symptomology Failed Back Surgery Syndrome* Osteoporosis* Urinary tract infection* Compression fracture* Somato-visceral mimicry syndrome*  Organic pathology (tumor, rheumatoid, endometriosis, arthritic disorders)* Leg length inequity*  Sacro-iliac dysfunction* Hip disorder*    **Disagreement in research as cause of low back symptomology Morbid obesity?**   OA = osteoarthritis Another problem is the hypothesis that a person who suffers with continuing bouts of low back pain may be predisposed, due to inactivity or inability to exercise, to gain weight thus increasing their BMI. This hypothesis to our knowledge, has yet to be fully discussed and investigated. Conclusion The data for a link between obesity and low back pain appears to be controversial. Yet, this does not adequately address the appropriate therapeutic approach to the obese patient with low back pain. The studies chosen for this review fail to document a definitive causal link between obesity and low back pain. Further research and epidemiologic data is needed to continue the search for a definitive answer. Competing interests The author(s) declare that they have no competing interests.