Study under review: Visceral adiposity and metabolic syndrome after very high–fat and low-fat isocaloric diets: a randomized controlled trial
Many controlled trials have compared low-carbohydrate to low-fat diets in their ability to promote weight loss. Among trials lasting longer than six months in duration, both diets appear similarly effective. However, another meta-analysis focusing exclusively on trials where the low-carbohydrate group consumed less than 120 grams of carbohydrates per day found that low-carbohydrate diets led to greater weight loss.
As the popularity of low-carbohydrate diets for the treatment of obesity continues to rise, there is still concern over their effects on metabolic health, particularly because of the potential for these diets to be high in saturated fat. For instance, even when participants with obesity are eating in a caloric deficit, consuming a diet high in saturated fat produces changes in skeletal muscle insulin signaling that may lead to insulin resistance over the long-term.
However, as we have learned in previous Study Deep Divess, not all food sources of macronutrients are the same. Study Deep Dives #9, Volume 1, Got milk (fat globule membrane), discussed a study in which a diet where the saturated fat was provided from cream led to more favorable blood lipid profile than an otherwise identical diet where the saturated fat came from butter. Similarly, in Study Deep Dives #8, Blast from the past: a paleo solution for type 2 diabetes, it was shown that a paleo diet was more effective than a diet based on the recommendations of the American Diabetes Association for improving insulin sensitivity, glycemic control, and blood lipids despite both diets having equal macronutrient composition (i.e., only food sources of macros differed).
A limitation of previous low-carb vs. low-fat studies is that food quality was largely uncontrolled for. Many people on a low-fat diet may eat more processed carbohydrates and added sugar while people on a low-carb diet may exclude these foods, only to drink buttered coffee every morning. Moreover, protein and polyunsaturated fat consumption, which are known to have profound effects on body composition and metabolic health, respectively, are not always controlled between low-fat and low-carb diets.
The current study sought to compare the effects of a low-carbohydrate diet (10% kcal) to a low-fat diet (less than 30% kcal) on body composition and metabolic health when both diets were minimally processed, based on the same foods, and had similar amounts of calories, protein, and polyunsaturated fat.
Both low-carbohydrate and low-fat diets are effective for promoting weight loss. However, effects on metabolic health continue to be an area of concern. The current study compared a low-fat to a low-carb diet, with the crucial difference from other research being that this study used diets that were both minimally processed, based on the same foods, and had similar amounts of calories, protein, and polyunsaturated fat.
Other Articles in Issue #26 (December 2016)
Gelatin + vitamin C + exercise = joint benefits?
Exercise can help remodel soft tissue, including the collagen in joint tissue. Researchers already knew that vitamin C and gelatin are involved in collagen formation, and here they are tested along with exercise in a randomized trial.
Can diet soda ruin your diet?
Evidence is still quite mixed when it comes to diet soda effects on weight loss (or gain). Observational evidence often contradicts with trial evidence. This study adds to the body of evidence, specifically on those with type 2 diabetes.
Interview: Dr. Taylor Wallace, PhD
Dr. Wallace has done research in a variety of areas, including anthocyanins in plants. Here, we ask him about topics ranging from food additives to supplement side effects.
Cut out FODMAPs, cut out IBS symptoms?
If you have IBS, you know that physicians often lack well-supported dietary recommendations, so new research can be extremely valuable. This study is the first meta-analysis on the low-FODMAP strategy for curbing IBS symptoms
Can probiotics help with Alzheimer’s?
With an aging population, more and more people know someone with Alzheimer’s. As a disease of the brain, symptoms could be helped by supporting an organ that plays directly into brain health: the gut.
Curcumin for a clear nose
There are two types of people in the world: those who get seasonal allergies, and those who don’t. If you sneeze and wheeze, this trial on curcumin for allergic rhinitis provides must-read information.
Interview: Grant Tinsley, PhD
Remember that neat intermittent fasting study in the previous issue of NERD? We were lucky enough to interview one of the study authors, Grant Tinsley.