How Effective Are Dietitians in Weight
Management? A Systematic Review and MetaAnalysis of Randomized Controlled Trials
While statistically significant, the mean change in weight and BMI due to the dietitian
intervention found in the meta-analysis was relatively small and of limited clinical significance at just
over one kilogram and 0.43 kg/m2, respectively.
…
The type of dietary advice provided by the dietitian in the intervention varied (shown in Table
2). Of the five interventions aimed at weight loss, four gave advice based on restricting energy intake,
by specifying a set intake of 3300KJ [30], calculating a 15% decrease in caloric intake [22], setting
energy intake at 80% of estimated requirements [21], or making individual prescriptions for an
energy deficit to achieve a loss of 0.5–1 kg per week [19]. The study by Kesman and colleagues
prescribed food portions rather than specifying energy and macronutrient intake [28]. Studies aimed
at preventing weight gain incorporated dietary advice to limit weight gain to within five pounds [29]
while a calculated energy increase was recommended in the study by Wolff and colleagues [31] to
allow for fetal growth. Of the studies assessing effects on weight or BMI, Rhodes and colleagues [23]
limited the proportion of energy supplied by fat and saturated fat [23], Wong and colleagues used
the Dietary Approaches to Stop Hypertension (DASH) diet goals [24] and Liu and colleagues
specified 10% caloric reduction to achieve weight loss but only in those with a BMI of 24 or above
[25]. All participants in the Liu study received the same advice on macronutrient distribution (fat
<30% calories, carbohydrate 55–65% calories and 20–30g of fiber/day.
My interpretation: people who are so motivated to lose weight that they will waste precious time listening to a dietitian are still able to lose a tiny amount of weight despite being told to do the opposite of what they ought to be doing.