What Do People (Want to) Eat After Bariatric Surgery?

The reason that medications and surgery work so much better for managing obesity than behavioural interventions alone, is because they change the underlying biology that drives weight gain and defends against weight loss. Thus, rather than relying on willpower, these treatments change ingestive behaviour by modifying the complex neuroendocrine pathways that regulate food intake. 

So what exactly do people who undergo bariatric surgery experience in terms of wanting and liking foods and how does their dietary intake change following surgery?

This is the topic of a systematic review and meta-analyses of food preference modifications after bariatric surgery by Erika Guyot and colleagues from the University Laval, Quebec, Canada, published in Obesity Reviews. 

Apart from the homeostatic control of energy intake, the authors remind us that,

Food intake is partly under the control of the reward system (tonsil, ventral tegmental area, hypothalamus, limbic system, and prefrontal cortex). This system assigns a hedonic value to food and generates motivation for food intake. Food reward has been shown to have two distinct components. The first component is “liking” and is related to the pleasure and the sensory properties of foods. The second component is “wanting”, which is related to the motivation and is defined as an implicit drive to eat.”  

Both of these components of food intake have been reported to be altered in patients post-surgery and imaging studies have shown a decrease in the potential of palatable foods’ ability to activate the relevant areas of the brain in post-surgical patients. 

The authors included 57 studies in their review (47 studies were prospective, 8 were cross-sectional, and 2 were longitudinal retrospective) that included 2,271 patients with RYGB and 903 patients with SG.

As expected, there was significant heterogeneity amongst the studies, which used a total of 16 different methods to assess food intake and preferences, with the majority being based on food records (N = 24), Food Frequency Questionnaires (FFQ) (N = 12), and food recalls (N = 11). Likewise, time points for assessment ranged from days to months post-surgery all the way up to 10 years later. 

Despite these methodological differences, a couple of important themes emerged.

Overall, despite a marked reduction in caloric intake, there was a significant increase in protein intake (from baseline), with a reduced intake of calories from fat. Carbohydrate intake, as a proportion of overall caloric intake, was largely unaltered. 

Perhaps more interestingly, several studies also described differences in food preferences. Thus, there appeared to be a postoperative decrease in preference for red meat, while other types of meat seemed unaffected. With regard to dairy, there appeared to be a preference for low-fat products. Changes in fruit and vegetable consumption appeared inconsistent, however, most studies found a lower postoperative preference for starchy foods and sweets. 

It should however be noted that most of these changes were reported in the first year after surgery, and whether or not these changes persist over time remains unclear. 

In terms of desirability of foods, the results point in the direction of a selective decrease in wanting for highly palatable foods after bariatric surgery, while there is an overall decrease in food preference and liking in the first postoperative months, which seems to be sustained up to 24 months for highly palatable foods only (high fat and sweet foods).

Overall, the authors conclude that, despite important limitations of these studies, 

“… food preferences in terms of macronutrient intake, food selection and overall food appreciation change following bariatric surgery and changes can be observed up to 5 years postoperatively. Especially, there was (i) a higher preference for proteins offsets by a lower preference for fats; (ii) a postoperative increased preference for healthy foods to the detriment of foods high in sugar, fat, salt and energy density; and (iii) overall decreased hedonic ratings, which in the longer term is seen for high fat and high sweet foods.”

How many of these changes are attributable to actual modulation of biological pathways and which may be the result of volitional or circumstantial factors, will require further investigation. 

I wonder what you have experienced or seen in your patients with regards to changes in food preferences.

Berlin, D