Strict diet explains metabolic effect of gastric bypass surgery

Date:
August 13, 2020
Source:
Lund University
Summary:
In many studies, bariatric surgery has been highlighted as an almost
magical method for weight loss and reversing type 2 diabetes. One
question that has remained largely unanswered is how the effect
of surgery differs from the effects of a strict low-calorie diet.



FULL STORY ==========================================================================
In many studies, bariatric surgery has been highlighted as an almost
magical method for weight loss and reversing type 2 diabetes. One question
that has remained largely unanswered is how the effect of surgery differs
from the effects of a strict low-calorie diet. This question has now
been examined by researchers at Lund University in Sweden in a study
published in the journal Diabetes.


==========================================================================
By monitoring individuals who underwent a six-week low-calorie diet
followed by a bariatric operation, they can for the first time show why
several health markers improve.

"What we previously thought was an effect of the operation is actually
due to the diet," says associate professor Nils Wierup, who led the
study with associate professor Peter Spe'gel.

In a bariatric operation, a so-called gastric bypass, a large part of the stomach and the first part of the small intestine are disconnected. The
patient needs to lose weight before the operation in order to reduce the
size of the liver and the amount of fat around the internal organs. This
is done to reduce the risk of complications.

Normally, the patient follows a strict six-week diet of fewer than 1 000 calories per day in order to achieve the weight loss. Previous research
has studied the combined effect of the diet and surgery. What has been
seen, in addition to weight loss, is improved blood sugar control, which
has been considered a result of an increase in the hormones GLP-1 and
GIP and enhanced insulin release. As a bonus, individuals with type 2
diabetes "recovered" just days after the procedure.

In a new study, researchers at the Lund University Diabetes Centre
(LUDC) and the Centre for Analysis and Synthesis (CAS) have for the
first time studied the effects of the strict low-calorie diet and the
operation separately. The results show that the diet alone accounted
for the greatest positive effect.



========================================================================== "More than 90 per cent of everything that occurred, happened as a result
of the diet. Very little changed after the surgery," says Peter Spe'gel,
who works at LUDC and CAS.

By measuring several hundred metabolites in the blood (substances formed
by, among other things, sugar, protein and fat in our metabolism) before
and after the low calorie diet and the operation, the researchers could
see that the levels of the various metabolites after the diet went in the direction expected from a reduced food intake and improved health. The
surgery itself caused very minor changes.

However, a few unique changes were observed that generally were the
opposite of those that happened during the diet. The researchers could
link some of these effects to the stress that surgery causes for the
patient, and this was supported by the fact that virtually all the
changes had disappeared six weeks after the operation.

The one most surprised by the results is Nils Wierup, who previously,
unlike Peter Spe'gel, was convinced that it was the surgical procedure
and the hormonal changes that accounted for the improved effect.

"What we previously thought was linked to the gastric bypass surgery is actually not. I have had to change my viewpoint," he says.



==========================================================================
"It was very good for this project that at the start we had such differing expectations and hypotheses on the effects bariatric surgery and diet have
on metabolism. We have therefore looked very carefully at all the results
to elucidate the study from all conceivable angles," adds Peter Spe'gel.

The results are not to be interpreted as the low-calorie diet being
beneficial in itself or that the operation is unnecessary. The procedure
is necessary in order for the patient to maintain a limited food intake
for a long period.

"A low-calorie diet is usually not harmful. The fact that we have now
shown the effects previously associated with surgery actually arise during
the preceding low-calorie diet, and not as a response to the surgery,
may perhaps make gastric bypass surgery less magical.

However, as a result of this, we can also point to bariatric surgery
not having any negative metabolic consequences," says Peter Spe'gel.

"If you are seriously overweight, calorie restriction is not necessarily harmful. Gastric bypass is a good treatment method for obesity. In
addition to the weight loss being more considerable and long-lasting
compared to a low- calorie diet, the surgery has the added effect that
the patient's diabetes reverses," states Nils Wierup.

The results also raise new questions.

"If metabolism is primarily affected by the diet and not the surgery, what
then is the function of the hormones GLP-1 and GIP?," says Nils Wierup.

The answers will possibly emerge from forthcoming studies in which the researchers will conduct a long-term follow up and compare their results
in a European study.


========================================================================== Story Source: Materials provided by Lund_University. Note: Content may
be edited for style and length.


========================================================================== Journal Reference:
1. Katharina Herzog, Johan Berggren, Mahmoud Al Majdoub, Claudia
Balderas
Arroyo, Andreas Lindqvist, Jan Hedenbro, Leif Groop, Nils Wierup,
Peter Spe'gel. Metabolic Effects of Gastric Bypass Surgery - is it
all about Calories? Diabetes, 2020; db200131 DOI: 10.2337/db20-0131 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/08/200813123603.htm

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