DUNEDIN, New Zealand
— Cutting consumption
of sugar produces a small but significant reduction in body weight for
adults, a new meta-analysis concludes [1]. The study found less
consistent evidence for this effect in children, but this is likely
because the kids in the included trials did not tend to comply with
advice to reduce intake of sugar-sweetened foods and drinks, say
Dr Lisa Te Morenga (University of Otago, Dunedin, New Zealand) and colleagues in their paper published online January 15, 2013 in
BMJ.
The review is accompanied by an editorial [2] by
Dr Walter C Willett (Harvard School of Public Health, Boston, MA) and
Dr David S Ludwig
(New Balance Foundation Obesity Prevention Center, Boston Children's
Hospital, MA), which concludes that the tide is beginning to turn
against sugar, with evidence continuing to accumulate that it is indeed
deleterious to health.
Sugar is not the only issue; there is the bigger problem of carbohydrate
quality. Large amounts of refined carbohydrates are also a problem.
"It's clear that sugar does have adverse effects, particularly in liquid form as sugar-sweetened drinks," Willett told
heartwire
. "This study addresses a piece of the
picture, the effect on weight gain. There is also a strong body of
evidence showing that sugar-sweetened beverages are related to type 2
diabetes. And sugar is not the only issue; there is the bigger problem
of carbohydrate quality. Large amounts of refined carbohydrates are also
a problem," he added.
This meta-analysis "and other evidence in the broader literature
suggest that sugar intake should be limited," say Willett and Ludwig
.
But the question remains as to what is a desirable limit, they note.
Current intake of added sugar in the US and UK is about 15% of total
energy, so the 2003
World Health Organization (WHO) aim of limiting intake to 10% "could be viewed as a realistic and practical goal." However, the
American Heart Association (AHA) suggests a limit of 5% of energy, "which would be more consistent with a goal for optimal health," they point out.
Refined Carbohydrates Just as Detrimental, Say Editorialists
Willett and Ludwig note that the meta-analysis by Te Morenga et al
was commissioned by the WHO, which is in the process of updating its
recommendations on intake of dietary sugars. The meta-analysis shows
that exchanging dietary sugars with other carbohydrates made no
difference to the changes in body weight that they saw, indicating that
highly processed carbohydrates are just as detrimental as sugar, say the
editorialists.
"Unfortunately, the 2003 WHO report disregarded evidence suggesting
that refined grain and potato products have metabolic effects comparable
to those of sugar," they note.
Actions are needed at many levels, Willett and Ludwig state. Efforts
to reduce sugar intake "are appropriate" but "should form part of a
broader effort to improve the quality of carbohydrates." This should
include educational programs, improvements in foods and drinks provided
in schools and work sites, and supplemental nutrition programs for
people with low incomes.
"This is analogous to what we see for fats in that the type of fat
you consume is really important. A similar picture is emerging for
carbohydrates; quality turns out to be really important," Willett
commented. "Another nuance," he says, "is the way we consume things,
because that affects the physiologic response." For example, eating a
whole fruit is much preferable to drinking fruit juice, he notes. "The
sugar in fruits is balanced out by the fiber and other nutrients, and it
takes time to be released. When we eat a whole apple or orange, we
limit our intake. If you are drinking fruit juice, you might have three
or four servings, but you would almost never eat three apples or oranges
in a row."
Reducing the amount of sugar consumed in drinks "deserves special
attention because of the strength of evidence and the ease with which
excessive sugar is consumed in this form," he and Ludwig state. Policy
approaches--such as imposing tax on sodas--are "useful," as are
restrictions on advertising to children and limits on serving sizes, as
have been tried in New York.
This is a global issue, with Coke and Pepsi pushing very hard, and the implications are horrendous.
"Sugar-sweetened beverages are such a big part of the picture," Willett commented to
heartwire
. "The average consumption among low-income
groups in the US is about three servings a day; it's huge. And this is a
global issue, with Coke and Pepsi pushing very hard, and the
implications are horrendous."
The AHA agrees,
showcasing in its top 10 advances of 2012 studies that illustrated the effect of
sugar-sweetened beverages on body weight in children.
Willett says physicians and other healthcare providers have an
important role to play "by routinely asking about consumption of
sugar-sweetened drinks as well as tobacco and alcohol use" and by
assuming leadership in public-health efforts to limit sugar as a source
of harm.
Advice to Cut Sugar Intake Important for Obesity Reduction Strategies
In their meta-analysis, Te Morenga and colleagues included the
results of 30 randomized controlled trials and 38 cohort studies of
dietary sugar intake and adiposity. Free sugars were defined as sugars
that are added to foods by the manufacturer, cook, or consumer, plus
those naturally present in honey, syrups, and fruit juices.
Healthcare providers could play an important role by routinely asking
about consumption of sugar-sweetened drinks as well as tobacco and
alcohol use.
In trials of adults with at-will--no strict control of food
intake--diets, reduced intake of dietary sugars was associated with a
small decrease in body weight (0.80 kg; p<0.001). Conversely,
increased sugar intake was associated with a comparable weight increase
(0.75 kg; p=0.001). Isoenergetic exchange of dietary sugars with other
carbohydrates showed no change in body weight.
Trials in children showed no overall change in body weight. But in
relation to intake of sodas, after one-year follow-up in prospective
studies, the odds ratio for being overweight or obese was 1.55 among the
groups with the highest intake compared with those with the lowest
intake, they note.
"It seems reasonable to conclude that advice relating to sugars is a
relevant component of a strategy to reduce the high risk of overweight
and obesity in most countries," the New Zealand group concludes.
Te Morenga et al have no conflicts of interest, nor do Willett and Ludwid.
