Probiotics Inhibit Ill-Health Effects of 7-Day Overfeeding in Man - Does This Make Yakult(R) the Perfect Tool in Your Bulking Toolbox or is it Just Another Marketing Gag?

Keep in mind: We are dealing with an industry sponsored study, here. One, w/ high baseline differences in insulin sensitivity between the groups.

Investigations into the effects of the intestinal microbiome are popping up all over the place. Unfortunately, many of the studies are conducted in rodents. Whether or not and if to which extent the results transfer to human studies is not sure, though.

Against that background, the results of a recent study from the Loughborough University are all the more intriguing. Why? Well, the study was conducted in a total of seventeen healthy subjects (fourteen males and three females) and the results of the study suggest that  probiotic supplementation may be useful in the prevention of diet-induced metabolic diseases such as type 2 diabetes.
Consumption of probiotic yogurt has already been shown to reduce fasting blood glucose concentrations and glycosylated Hb levels in type 2 diabetic patients (Ejtahed. 2012), but whether or not probiotics can also prevent diet-induced insulin resistance in otherwise healthy subjects is not yet known. Therefore, Hulston et al. tested the hypothesis that 4 weeks of supplementation with probiotics (Lactobacillus casei Shirota (LcS)) would prevent insulin resistance induced by short-term, high-fat, overfeeding in healthy young males and females.

Table 1: Physical characteristics of the study subjects before and after 7 d of overeating (Hulston. 2015).

The subjects, seventeen healthy subjects (fourteen males and three females; Table 1), were randomly assigned to one of the following two groups: A control group (n=9, seven males and two females),  and  a probiotic group (n=8, seven males and one female). The probiotic that was used in the present study was LcS (commercially available as the fermented milk drink Yakult Light).

"Both groups maintained their habitual food intake during the first 3 weeks of the study (days 1–21); however, the probiotic group also consumed 65 ml of Yakult Light twice each day. An oral glucose tolerance test (OGTT) was performed on day 22 for the assessment of baseline insulin sensitivity" (Hulston. 2015).

After completing the first OGTT, subjects were provided with a high-fat (65 % energy), high-energy (approximately 50 % increase in energy intake) diet for 7 d. The probiotic group continued to consume 65 ml of Yakult Light twice throughout the 7 d overfeeding period. We selected a 4-week LcS supplementation period, as previous experiments have demonstrated that this is sufficient to alter the composition of the gut microbiota in humans.

Figure 1: Baseline and overfeeding macronutrient intake (left) and insulin sensitivity before and after the 7-day overfeeding period in the 17 healthy, normal-weight sedentary study participants (Hulston. 2015).

Next to a weight increase which did not differ for the two groups, the researchers found significant changes in fasting plasma glucose concentrations in response to the 7 d of overfeeding protocol, changes that reflect (a) the overall increase in carbohydrate consumption and (b) the decrease in insulin sensitivity which was measured separately in response to the meals and yielded a significant reduction of 27% from albeit high baseline levels in the supplementation group and no significant difference in the probiotic group.

With a study period of only 7 days, the overfeeding did yet not wreak enough havoc to mess with the fasting serum insulin concentrations, the hallmark feature of beginning diabetes. The latter remained stable in both both groups - more evidence that you can neither get fat, nor diabetic in just a few days (reread my article "Can You Get Fat in Only Three Days?" | here).
References:

• Ejtahed, Hanie S., et al. "Probiotic yogurt improves antioxidant status in type 2 diabetic patients." Nutrition 28.5 (2012): 539-543.
• Hulston, Carl J., Amelia A. Churnside, and Michelle C. Venables. "Probiotic supplementation prevents high-fat, overfeeding-induced insulin resistance in human subjects." British Journal of Nutrition (2015): 1-7.