Whey is well known as the gold standard in proteins, but what a lot of people don't know is that soy isolate is hot on its heels. The fact that this plant-based protein is nearly indistinguishable from whey when it comes to quality, digestibility, and amino acid balance comes as a surprise to many, as does the negligible isoflavone content – the phytoestrogens present in raw soybeans are largely removed from the soy isolate during processing.
Protein and Weight Loss
Protein supplementation used to be the sole domain of people trying to build muscle, but word is getting out that protein has a lot of benefits for people trying to lose weight.
Firstly, protein is filling and helps curb the appetite. Secondly, the body actually uses a lot of energy digesting protein - about 30% of the energy consumed, unlike fat and carbs, which are digested much more efficiently. This is known as the 'Thermic effect'. On top of this, protein helps the body retain and build muscle. Unlike fat, muscle tissue is metabolically active, so people with more muscle tissue use more energy at rest, which can help keep the weight off in the long term.
For these reasons, a low fat, low carb whey protein is often recommended to help dieters meet their weight loss goals. But can soy protein be just as effective for weight loss? Surprisingly, there really hasn't been any investigation into this until now.
Can Soy Support Weight Loss?
A recent study took a group of obese men and women, and randomly split the participants into two groups. One group recieved a non-soy protein based meal replacement supplement, the other group recieved soy protein, and members of both groups received pre-prepared calorie controlled meals tailored to their individual energy needs.
The participants stuck to these diets for twelve weeks. At the end of the twelve weeks, the researchers looked at body composition and cardiac risk factors, and found that there was no difference in the amount of weight lost or the body composition between the two groups.
What about Heart Health?
The researchers also found an identical reduction in cardiac risk factors between the two groups, with one exception - the non-soy group showed a greater reduction in diastolic blood pressure than the soy group, but this wasn't large. The researchers also measured the strength and physical performance of the study participants, and found no differences between the two groups. They also found no change from the beginning to the end of the study. This reinforces something we already know - protein alone won't build strength or muscle. There is no getting around the fact that the key to improvement in these areas is training.
A lot of people use soy protein, including those with milk allergies, vegans, and people who prefer a plant-based protein. This study has shown that soy is just as effective as dairy-based proteins for weight loss, which will be of interest to the steadily growing number of people who are using a high protein diet to lose weight.
Beavers KM, Gordon MM, Easter L, Beavers DP, Hairston KG, Nicklas BJ, Vitolins MZ. Effect of Protein Source during Weight Loss on Body Composition, Cardiometabolic Risk and Physical Performance in Abdominally Obese, Older Adults: A Pilot Feeding Study. J Nutr Health Aging. 2015;19(1):87-95.