Study under review: The impact of starchy food structure on postprandial glycemic response and appetite: a systematic review with meta-analysis of randomized crossover trials
The human body often experiences changes in blood glucose and insulin in response to food consumption, which is called the glycemic response. The glycemic response to individual foods is an important aspect of managing metabolic diseases, such as type 2 diabetes. Carbohydrates are the primary food constituent that elicit a glycemic response, and starch constitutes the majority of carbohydrate intake in most diets. The precise effect that a given starchy food has on the glycemic response depends on the extent and rate (i.e. fast or slow) of starch digestion. Insulin levels in the blood tend to correlate with this effect, such that carbohydrate-laden foods that cause fast, large increases in blood glucose also tend to cause fast, large increases in circulating insulin.
The structure of a starchy food is known to regulate the extent to which a starch is digested, as well as the rate at which it is digested. Much of the structural differences in starch sources can be observed at the microstructural level (less than 100 μm), which is mostly determined by different molecular structures of starch. There are two primary forms of starch: amylopectin and amylose. As shown in Figure 1, amylopectin has a highly branched structure, similar to glycogen, whereas amylose has a more linear structure, similar to cellulose. The branched structure of amylose allows it to be digested more rapidly and more completely due to the fact that there are more bonds accessible to enzymes for digestion. There are also other microstructural aspects that can affect digestibility, such as gelatinization, retrogradation, interactions with lipids and proteins, and whether a carbohydrate source has intact cell walls or not.
Other Articles in Issue #82 (August 2021)
Citrulline malate may help you pump out a few extra reps
According to this meta-analysis, taking six to eight grams before a resistance training session could help crank out a few more reps. There was some evidence of publication bias, though.
Does exercise affect fat mass differently than a caloric deficit?
This review suggests that exercise alone can help people lose proportionally more visceral fat compared to dieting or dieting plus exercise. However, some nuances in how the study was analyzed make it difficult to put much faith in this finding.
Nulls: May–June 2021
Here's a quick roundup of studies that looked for evidence of efficacy but came up empty-handed.
Mini: When are lifestyle changes enough to treat high blood pressure and cholesterol?
We give a quick rundown of a recent scientific statement from the American Heart Association on the impact of lifestyle changes on blood pressure and cholesterol.
Can beer hit the ‘pause’ button on menopause symptoms?
While this study found that beer could help with what ales people with menopausal symptoms, design and reporting issues hold this study back from being pitcher perfect.
Deeper Dive: Melatonin mysteries — can supplementation decrease circadian misalignment and body weight in night shift workers?
There was no apparent effect compared to placebo, but the study still hints at a positive impact.
Beyond strict meal planning: dietary flexibility won’t hurt body composition goals
This study suggests that people looking to shed some fat for physique can do equally well with flexible and rigid diet plans.