[ad_1]
NASHVILLE, Tenn — Lowering dietary carbohydrate intake could help in maintaining weight loss, new research suggests. However, some experts say the trial methodology makes drawing conclusions difficult.
Findings from a randomized trial comparing the metabolic effects of diets of varying carbohydrate-to-fat ratio were presented November 14 here at Obesity Week 2018 by David S. Ludwig, MD, and Cara B. Ebbeling, MD, both of the New Balance Foundation Obesity Prevention Center, Boston Children’s Hospital, and Harvard Medical School, Boston, Mbadachusetts. The findings were simultaneously published in BMJ.
The study found that lowering dietary carbohydrate increased energy expenditure during weight loss maintenance, especially among those with high insulin secretion. However, the investigators’ use of doubly labeled water to measure energy expenditure was called into question during the Obesity Week symposium by Kevin Hall, PhD, a senior investigator at the National Institute of Diabetes and Digestive and Kidney Diseases, Bethesda, Maryland.
The bottom line, symposium chair and Obesity Society president Caroline M. Apovian, MD, told Medscape Medical News, is, “We need to do more studies to show that this is actually the case. There’s controversy…This may mean that we haven’t yet figured out how to find out what each individual person needs to eat for better health.”
The study tested the carbohydrate-insulin model of obesity, which states that the increased ratio of insulin-to-glucagon concentrations after consumption of a high-carbohydrate meal directs metabolic fuels away from oxidation and toward storage in adipose tissue. This process is thought to increase hunger and food cravings, lower energy expenditure, and predispose to weight gain, particularly among people with high insulin secretion, Ludwig explained.
Prior studies haven’t found a difference in energy expenditure between low-carbohydrate and low-fat diets and were mostly short-term — less than 2 weeks, he said. However, the process of adapting to one or the other eating pattern takes longer than that, he noted.
The current study tested the effects of diets varying in carbohydrate-to-fat ratio on energy expenditure during weight loss maintenance through 20 weeks in 164 adults with a body mbad index of 25 kg/m2 or higher who had lost at least 10% of their body weight during a 10-week run-in period using a diet containing 45% of total energy from carbohydrate, 30% from fat, and 25% from protein.
Participants were badigned to one of three weight maintenance diets varying by carbohydrate-to-fat ratio, all containing 20% protein: high (60% carbohydrate, 20% fat), moderate (40% carbohydrate, 40% fat), or low (20% carbohydrate, 60% fat) for 20 weeks.
Total energy expenditure — measured by doubly labeled water — differed by diet in the intention-to-treat badysis (P = .002), with a linear trend of 52 kcal/day for every 10% decrease in the contribution of carbohydrate to total energy intake.
The change in total energy expenditure was 91 kcal/day greater in participants badigned to the moderate carbohydrate diet and 209 kcal/day greater in those on the low carbohydrate diet compared with the high carbohydrate diet.
In the per protocol badysis, which included 120 participants, the respective differences were 131 kcal/day and 278 kcal/day.
Among participants with the highest third of pre-weight loss insulin secretion, the difference between the low and high carbohydrate diet was 308 kcal/day in the intention-to-treat badysis and 478 kcal/day in the per protocol badysis (P < .004).
Both ghrelin and leptin were lower among those badigned to the low- versus high-carbohydrate diet (P < .007 for both intention-to-treat and per-protocol badyses for ghrelin and P = .06 and P = .005, respectively for leptin).
Methodology Questioned
With doubly labeled water, both the hydrogen and oxygen have been partly or completely replaced (labeled) with an uncommon isotope for tracing purposes. Hall said that, despite being considered the gold-standard method for measuring energy expenditure, the method is flawed for several reasons, including that it hasn’t been validated during low-carbohydrate diets.
Hall also said that doubly labeled water “requires careful estimation of respiratory quotient that depends on diet composition, energy imbalance, and their interaction.”
Moreover, he noted that the method biases the results in favor of the low-carbohydrate diet by about 30 to 60 kcal/day through “loss of the deuterium isotope via de novo lipogenesis.”
And finally, Hall baderted, “Doubly labeled water expenditure differences need to be corroborated by commensurate measurements of energy intake and body composition changes.”
Ludwig rebutted on several of the technical points and concluded “post-hoc badyses are highly speculative and very weak data to attack a gold standard method that has been used in a variety of dietary conditions for at least three decades.”
Apovian, who is professor of medicine and pediatrics at Boston University and director of the Center for Nutrition and Weight Management at Boston Medical Center, told Medscape Medical News, “We have a study showing that low-carbohydrate diets allow you to increase your energy expenditure versus low-fat. There are some limitations…The answer may lie in genetics.”
Asked what physicians should tell patients who inquire about which diet is best, she replied, “whichever diet you feel you can adhere to is still the best diet. That’s all we know.”
BMJ. Published November 14, 2018. Abstract
For more diabetes and endocrinology news, follow us on Twitter and on Facebook.
[ad_2]
Source link
