Why Soy Protein is in Fact an Awesome Food for Weight Loss

Soy protein is a great low carb, low fat, weight loss food choice.

There has been much debate about soy protein and its effects on health.
The latest ‘cutting edge’ research strongly supports the idea that soy has been unfairly maligned, based on half truths and a lack of understanding of the complexities of human physiology.

Misinformation and misunderstandings abound in the realm of internet ‘science’.

Before we come to some of the claims made against soy and the rebuttal to these claims; a few facts about soy.

Soy protein, extracted from the soybean plant has been in the food chain for over 5,000 years,

Soy protein has the highest possible score of protein quality. The PDCAAS is the standard measurement of protein quality.

It provides all the amino acids, in the ideal ratio, needed to support health.

Soy also provides a good amount of potassium, zinc, iron, vitamin-E, phosphorous as well as the full vitamin B-complex.

Soy protein has high amounts of the amino acids arginine and glutamine. (Both of these amino acids have been purported to have beneficial metabolic effects)

Arginine is well known as a stimulant of anabolic hormones that stimulate muscle formation.

Soy milk also has a good amount of the super nutrient -alpha-lipoic acid (ALA).
ALA is a fatty acid which improves metabolic function and appetite control.
It has also been show to fight oxidative stress and inflammation.

Some soy milk products contain upwards of 300mg of ALA; a serving of 2% milk contains only 20mg of ALA.

Supplemental soy comes in three types: soy protein concentrate, soy protein isolate and textured soy protein.

Carbohydrates are removed from soy protein isolates so there is less of a soy-bean taste with this particular form.

Textured soy protein is what is used to make the various vegetarian food products.
These are about 15% (non-fibre) carbohydrates - which is still low. 

Claim : Soy contributes phytoestrogens and will therefore make men develop female characteristics and lead to decreases in testosterone.

​An important point to make in favour of Soy is that most of the adverse effects have been seen in rodent studies. 


A new study from the Netherlands sheds light on why this may be the case.


Rats breast tissue activates soy isoflavones at a rate 30 times more than humans, leading to an extreme and unhealthy hormonal effect that is not seen in humans.


We really need to look at human specific studies if we want to see the true effects of soy for HUMANS.

The latest studies into soy protein support the idea that it does NOT decrease testosterone and raise oestrogen, in humans. 

Researchers found that daily supplementation of 50g soy protein, over a 12 week period of whey or a soy/whey blend resulted in an increase in lean body mass and did not negatively affect testosterone or estradiol levels in 41 male athletes engaging in a weight-training program.

A 2001 study found no change in testosterone with soy consumption.

Claim 2: Soy protein intake adversely affects muscle growth.

Three studies actually looked at the effects of supplementing with animal protein vs. soy protein during a resistance training program in humans.

It was shown that there were ‘no significant differences in strength, hypertrophy, muscle cross-sectional area, or muscle creatine levels when comparing meat protein vs. soy protein consumption during resistance training

In a 2006 study, it was concluded that ‘protein supplementation increase muscle strength and size, independent of the protein source.’

In another study looking at the effects of a whey and soy supplemented diet in mice found that both protein sources had positive effects on antioxidant status and resulted in enhanced body composition.

A comparison between whey and soy protein bars in college males in a weight training class, found that both protein sources led to greater gains in lean body mass, however, only the soy protein preserved two aspects of antioxidant function, whereas the whey protein did not counteract the oxidative stress of exercise as effectively

Claim 2: Soy creates metabolic health problems and contributes to weight gain.

In fact, the preponderance of studies show that the very opposite is true. Soy is in fact very beneficial for metabolic health and weight loss.

A study carried out in Iran, found that compared to the placebo group, women who received soy supplements had lower levels of circulating insulin in the blood.

They also had lower levels of testosterone, (high testosterone is clearly not desirable in women), low levels of harmful LDL cholesterol and triglycerides, or fats in the blood, than the participants who received the placebo.

All these effects are indicators of how well hypothalamus in the brain is functioning. (The hypothalamus in the brain controls the function of whole panoply of bodily health systems).

Body weight is also one of the systems controlled by this part of the brain.
If soy improves all these symptoms, it must be improving hypothalamic function in the brain.
A well functioning hypothalamus would inevitably mean improved appetite control and increased fat burning.

Although soy has this balancing effect on hormone levels in women by reducing unwanted high testosterone it doesn’t mean the same would occur in men.
Soy corrects the hypothalamus in the brain to put hormones in their right order.

A couple of studies have found that soy protein actually led to greater reductions in body fat content and blood glucose levels compared to casein or whey protein.

Research shows that when soy consumption goes up, weight goes down.

New research on teenagers shows choosing a high-protein, soy-based snack vs. no snacking helped curb hunger longer, reduced confusion-bewilderment and increased cognitive flexibility.

Leptin-Like Effects of Soy in the Brain 

In order to try to fathom the mechanism of soy in improving appetite control; a new university study compared the effects of soy protein peptides with those of leptin.

Leptin is the master satiety hormone released by our fat cells which tells us we’re full and we don’t need to eat any more

The researchers  injected leptin and soy peptides directly in to the brain and compared the effects.

They found that soy did enact the same mechanisms in the brain as leptin.

Soy peptides had a similar effect to leptin action in the brain!!

After the third injection, the researchers noticed a significant weight loss in the group of animals that had received one of the soy hydrolysates, even though the animals hadn't changed their eating habits.
In this instance, soy protein appeared to have caused weight loss not by reducing food intake but by altering the rats' metabolism.

The lead researcher of this study concluded that soy contains anorectic peptides that signal a feeling of satiety as well as peptides that boost the metabolism.

Another study found that a low calorie soy protein supplemented group experienced significantly greater reductions in weight, fat mass and waist circumference over the 12 week trial than did the low calorie non- soya group controls.

Furthermore, total and LDL serum cholesterol were changed to a greater extent than expected given the amount of weight loss, suggesting that soy protein, phospholipids, fibre, or other elements may reduce serum cholesterol independent of weight loss.

The soy supplemented group also reported a greater reduction in appetite

A recent Chinese study found it is also effective in assisting with weight loss and muscle mass gains.

Half of the 60 overweight participants were instructed to drink a bottle of 450ml sugar-free soy milk 30 minutes before lunch and dinner, as well as 30 minutes after a workout, for three consecutive months. The remaining 30 participants were in a control group.

“Participants in the soy milk experiment group noticed a significant decrease in their waistline, body-fat ratio, visceral fat, blood sugar level and blood pressure by the end of the research,”

Hsiao, who oversaw the study, said participants’ body fat dropped nearly 3 percent on average and that they lost 1.4kg more than those in the control group.

During the three month period, one study participant, a male surnamed Liu, “lost 13.7kg and saw his body-fat ratio fall from 27.3 percent to 23.5 percent”

Soy Fibre Helps 

Another study examined the effects of soy fiber (SF) on body weight, body composition, and blood lipids in overweight and obese participants.

Thirty-nine overweight and obese college adults (19-39 years of age) were randomly assigned to consume control biscuits or biscuits supplemented with SF for their breakfast for 12 wk (approximately 100 g/day).

There were significant differences in changes on body weight, BMI, and LDL-cholesterol (LDL-C) between the two groups after 12-wk intervention (p < 0.05).

"Waist circumference blood pressure, and glucose, body fat, and trunk fat of participants in SF group were observed significantly after 12 wk."

Soy Anthocyanins Help Too

The effect of anthocyanins extracted from black soybean on body weight, adipose tissue weight, and serum lipid was evaluated in rats fed the high fat diet.

Weight gain was significantly lowered in the rats fed HFD plus black soybean anthocyanins compared with the rats fed HFD alone.
The weight of organs or tissues including liver, adipose fat tissues was decreased in rats fed anthocyanins compared with the rats fed HFD.

The black soybean anthocyanins added diet also reduced the levels of triglyceride (TG) and cholesterol in the blood and increased HDL- cholesterol level of rats fed HFD.

Another study showed that consuming soy protein rich in isoflavones decreases fat deposition (storage) while increasing muscle mass.

This is especially important since lean muscle tissue burns up to 17 times more calories than the same amount of fat tissue, even at rest.

Soy For Women 

The European Food Safety Authority (EFSA) confirmed  that soy isoflavones, or phytoestrogens, are safe with no negative effects on mammary glands, uterus or thyroid, adding to a growing body of evidence that shows women can benefit from phytoestrogens and relieve menopause symptoms, such as hot flashes

At 105 mg of isoflavones daily, or about four servings of traditional soy foods, over a 50-day period, women increased bone calcium retention by 7.6 percent, showing that soy is an effective bone-preserving agent. The study found benefit even when lower amounts of soy foods were consumed.

About 10 percent of women in the U.S. develop gestational diabetes, or high blood sugar, during pregnancy.
A clinical study found that a diet with increased soy protein for six weeks of pregnancy significantly lowers fasting blood sugar, insulin levels, and fat circulating in the blood.

Since these are all symptoms of the hypothalamic down regulation which can occur during pregnancy, it is almost certain that soy would also therefore improve appetite control, metabolism and fat burning, similarly. 

A large-scale  study at a Boston fertility centre showed female consumption of soy, improved birth rates for couples undergoing fertility treatment.

For men, soy intake had no negative impact on fertility

Researchers in Japan found that soy protein prevented the weakening of skeletal muscle caused by immobilization or sedentary lifestyles!!

Soy Protein and Cancer 

A Chinese study analyzing isoflavone levels in the blood discovered that those who consumed soy had the lowest likelihood of developing prostate cancer, and, even more, soy greatly reduced the risk of the cancer metastasizing, or spreading throughout the body.

Researchers at The Ohio State University found that soy decreases multiple inflammatory markers that can impact prostate cancer and progression, including reducing infections.
Early stage prostate cancer patients had 68 mg soy isoflavones daily for eight weeks via soy flour bread.
Soy intake led to an improved immune system response, reduced inflammation related to early development of cancer cells, and encouraged an active immune system throughout cancer progression.

University of Washington doctors determined that high soy consumption has no effect on women getting breast cancer for the first time, and, even more, discovered that women who eat a lot of soy foods have reduced risk of breast cancer recurrence.

Another study found that in young girls, high levels of soy isoflavone genistein along with low exposure to BPA showed long-term decreased risk of breast, gynaecological, oesophageal, lung and urological cancers, cardiovascular disease and Alzheimer’s disease.

Researchers in Japan evaluated more than 30,000 men and women, over a period of 15 years, and found people that consumed the most soy foods had a significantly decreased relative risk of stomach cancer, the leading cause of cancer-related deaths.
Specifically, higher intakes of non-fermented soy foods such as tofu, soymilk and edamame were significantly associated with a lower risk of stomach cancer and were found to actually have a protective effect against developing the cancer.

Other researchers also concluded that soy intake prevents premature puberty:
Soy is actually protective and higher soy intake may lead to later puberty” because the oestrogen mimicking effects of soy may “down-regulate the oestrogen receptor, so that later in life, your body doesn’t perceive or see oestrogen in quite the same way.”

Soy Lowers Bad Cholesterol 

It has been known for some time that soy protein helps lower cholesterol.
But a 2015 meta-analysis showed soy significantly lowered LDL-cholesterol by 4.8 percent and lowered triglycerides by 4.9 percent, with even great impact for people who were diabetic or hypertensive – reducing LDL-cholesterol by 7.5 percent.

Soy is Cheaper Than Whey Protein 

Soy protein powder is considerably less expensive than whey and considering that soy has proven itself to be as beneficial for weight reduction and the improvement of other health measures as whey (if not more so), then choosing soy may just save you small fortune over time, with no loss (even improvement) to your general health and weight control. 

To find out more truths about how the body interacts with food to lead to weight loss or weight gain and poor health, you could start by signing up to receive my free dietary fat report, which gives you the low down on how different dietary fats affect our weight loss efforts and health (based on a comprehensive analysis of the science).

You can also read about the new science behind why intermittent abstinence from carbs can be a beneficial thing for weight loss and health in my blog post; The New Science of Low Carb 

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