Background: In 2013, the Swedish Council on Health Technology Assessment (SBU) published a report "Dietary treatment of obesity" where low carbohydrate diet (LCD) was established as one of the evidence based diet options in obesity treatment, even without diabetes. No data exists on how much the health care professionals (HCP) in primary care actually are informed of or to which extent they use the knowledge in the new report. We aimed to investigate the HCPs' current knowledge, attitudes and application of LCD in obesity treatment in primary care. Methods: All primary health care centres (PHCC) in Jönköping County Council (JCC) were invited to participate in this cross sectional descriptive study. HCPs who were working with obese patients were sent an online survey by email from January to March 2014. Data was collected about self-estimated knowledge, clinical practice of dietary advice and attitudes on LCD as well as demographic data and work related information. Chi2 and logistic regression were used to analyse associations between the independent and the outcome variables. Results: Two hundred and seventy-one HCPs completed the survey (70.7 %); 95 % gave dietary advice. Those who gave dietary advice, 49 % were uncertain about evidence based dietary advice; 28 % received education on dietary advice last year; 60 % reported patient requests for LCD; 80 % felt hesitant about LCD; 54 % stated that they have good knowledge about LCD and 47 % recommended LCD. Factors that influenced the advisement on LCD were profession (physician and diabetes nurse), patient requests for LCD (OR 0.46, 95 % CI 0.27-0.77, p = 0.003) and good knowledge (self-estimated) about LCD (OR 0.43, 95 % CI 0.26-0.71, p = 0.001). Recent education on dietary advice affected in a positive way the uncertainty about evidence based dietary advice (OR 0.19, p = 0.0001), the hesitancy about LCD (OR 0.37,, p = 0.002) and self-estimated knowledge about LCD (OR 2.67, 95 % CI 1.49-4.80, p = 0.001). Conclusions: HCPs were positive to dietary advisement but had an ambivalent attitude toward LCD as yet another dietary option. This area may be improved with continuous educational training, supposing that this is prioritized. Thus, it is reasonable to believe that LCD will gradually be more common as a tool to deal with obesity in primary care in the future.