This Summary of Recommendations and Evidence synthesizes the Key Practice Point(s) for each Practice Question (PQ) in this Knowledge Pathway. It is organized by the Nutrition Care Process and contains statements or recommendations that have been graded using either the PEN
approaches to critical appraisal. For additional information on the evidence and references, see the PQs in this Knowledge Pathway
As part of the PEN evidence synthesis process, the research in an area is reviewed, as well as various national recommendations. The most recent national recommendations do not typically supersede other evidence, as these recommendations are country-specific. PEN recommendations are based on evidence. Government agencies' recommendations are based on their assessment of the evidence in light of the populations served, risk and their ability to implement and monitor recommendations. These recommendations may not be based on a rigorously conducted systematic review. Country-specific recommendations, as well as PEN’s synthesis of the best evidence, are presented in the Key Practice Point for the PEN user to use at their discretion.
- The Effect on Appetite, Body Weight and Blood Lipid Levels
- The Effect on Glycemic Control in Individuals with Diabetes
1. The Effect on Appetite, Body Weight and Blood Lipid Levels
Appetite and Body Weight
Limited evidence suggests that cannabis may lessen weight gain, attenuate the increase in insulin and may alter blood concentrations of hormones associated with hunger (e.g. ghrelin, GLP-1) in adults who use recreational cannabis.
Limited evidence also suggests that medical cannabis does not impact appetite or body weight in adults with anorexia-cachexia and that cannabidiol (CBD) may reduce appetite in individuals with certain health conditions, such as rare forms of epilepsy.
Overall, more research on cannabis’ effect on appetite and body weight is needed.
A 2021 systematic review and meta-analysis of five RCTs (n=934) found that medical cannabis had no statistically significant impact on appetite, body weight or quality of life compared to placebo or pharmacologic appetite stimulant in adults with anorexia-cachexia due to HIV/AIDS or advanced cancer. Findings may be limited by small sample sizes, short study durations and the poor quality of the evidence, and may not be generalizable beyond white, middle-aged males.
A 2019 systematic review of 11 RCTs found that CBD (5 mg/kg/day to 750 mg twice a day) generally reduced appetite but had no effect on body weight. Half of the studies were conducted in individuals (including young children) with rare epilepsy. It was unclear how appetite was assessed in many studies and CBD was typically an add-on treatment with a wide variation in doses, which may limit these findings.
A 2020 RCT of 20 healthy adult cannabis users (aged 28±8 years, 75% male) found that cannabis (active dose tetrahydrocannabidiol (THC) 6.9±0.95% ≈50.6 mg) altered blood concentrations of certain endocrine markers. Compared to placebo, ingested, smoked and vaped cannabis all reduced the increase in blood insulin concentration over 90 minutes and resulted in lower blood concentrations of GLP-1. Total ghrelin was higher following oral cannabis compared to smoked or vaped cannabis. Cannabis did not have a significant impact on acyl-ghrelin or leptin and adverse events were not reported. Results may be limited by the small sample size, low number of female participants, the limited number of biomarkers measured, the exclusion of non-cannabis users, the lack of investigation of clinical and/or behavioural implications, the dose of cannabis used, which may not have been high enough to change appetite, and that the rigorous control of the study setting was not reflective of real-world settings.
A 2019 observational study of a nationally representative cohort of U.S. adults found that BMI increased over three years for all subgroups but that, compared to non-users, the increase in BMI was less for persistent cannabis users, followed by those who had initiated cannabis use in the preceding three years and then those who had stopped cannabis use in the preceding three years. Results may be limited by the use of self-reported anthropometric measures and statistical methods that may have reduced precision and introduced bias.Grade of Evidence C
CBD and THC are phytocannabinoids found in cannabis. THC is responsible for its psychoactive effects.
The mechanism through which cannabis may affect appetite and body weight is not known. It may mimic the action of endogenous cannabinoids in the hypothalamus that regulate energy balance, downregulate cannabinoid receptors involved in appetite regulation and/or reduce inflammation.
GLP-1 and ghrelin are both hormones, with the former being involved in insulin and glucose metabolism and the latter being involved in appetite, hunger and glycose homeostasis. There appears to be a synergistic effect between endocannabinoids and ghrelin, but the underlying mechanism is not clear.
Limited evidence from one narrative review suggests that individuals who smoke cannabis recreationally may have marginally higher HDL cholesterol and slightly lower triglycerides compared to non-cannabis smokers, but study limitations prevent a recommendation from being made.
Results from a 2019 narrative review suggest that individuals who smoke cannabis recreationally may have marginally higher HDL cholesterol and slightly lower triglycerides compared to non-cannabis smokers, but the results are not conclusive. Results may be limited by the observational study design, low methodological quality (e.g. small sample size, poorly controlled), the inconsistent definitions of “cannabis user,” the lack of reporting on cannabinoids and that modes of cannabis consumption beyond smoking were not considered.Grade of Evidence C
Cannabis’ purported benefits to blood lipids may be due to its ability to bind to cannabinoid receptor type 1 in the body, thereby blocking the binding of endocannabinoids, which are involved in hunger and body weight regulation.2. The Effect on Glycemic Control in Individuals with Diabetes
Limited evidence from observational studies suggests that recreational cannabis use is associated with an elevated A1C, an increased risk for diabetic ketoacidosis (DKA) and poorer self-management behaviours in adolescents and adults with type 1 diabetes (T1DM) and that it is associated with an increased risk for diabetes complications (e.g. arterial occlusion, myocardial infarction, renal disease) in adults with type 2 diabetes (T2DM). High quality evidence on this topic is lacking.
A 2020 rapid literature review found that:
- individuals with T1DM who used recreational cannabis had a higher A1C, a higher risk of DKA and poorer self-management behaviours compared to non-users
- individuals with T2DM who used recreational cannabis had a higher risk of diabetes complications (e.g. arterial occlusion, myocardial infarction, renal disease) compared to non-users.
Findings may be limited by the poor quality of the research (including the use of non-peer reviewed conference abstracts), inadequate reporting on diabetes treatment, cannabis consumption frequency, and the mode and the lack of reporting on the type of cannabis consumed.
Diabetes Canada developed a position statement based on the results from the preceding narrative review and recommends that adolescents and adults with diabetes do not use recreational cannabis due to the lack of evidence on its safety and because regular cannabis use is associated with poorer glycemic control, poorer self-management behaviours and more diabetes-related complications.
A 2020 cross-sectional study of 932 adults with T1DM found that those who used cannabis at least moderately were 2.5 times more likely to experience DKA compared to low and non-users. Results may be limited by differences in cannabis users and non-users (e.g. age, sex, educational attainment, length of T1DM diagnosis), the potential bias in self-reported data, potential confounding by risk for depression and that information about diabetes self-management, insulin regimen compliance and frequency of DKA was not collected.
A 2019 narrative review found that cannabis use in adolescents and adults with T1DM was associated with higher A1C values, an increased risk of DKA and changes to self-management of blood glucose (e.g. forgetting to take insulin, monitoring blood sugars more frequently). The results may be limited by the overall paucity of research and by the observational design of the included studies.Grade of Evidence C
The mechanism through which cannabis impacts glycemic control is not known but it may be because tetrahydrocannabidiol (THC) alters judgement and leads to poorer self-management behaviours or because recreational cannabis use is associated with unhealthy behaviours (e.g. smoking tobacco, eating a high fat diet) that may lead to poor metabolic outcomes. The cannabinoids in cannabis may change gut motility which, in combination with cannabis impairing self-management behaviours, may explain the increased risk of DKA.