Diet reality check: Does soy make you fat, as Blake Lively suggests?

Blake Lively cut out soy to get her post-baby body in bikini-shape for The Shallows. Here's a reality check on her diet from health experts. Photo by Tristan Fewings/Getty Images

Blake Lively got into the best shape of her life for The Shallows, filmed just eight months after she gave birth to her daughter with husband Ryan Reynolds.

The 28-year-old actress, who’s pregnant with her second child, credited her post-baby bikini body to cutting gluten and soy. She focused on the latter when explaining the reasoning behind the diet.

“Once you remove soy, you realize you’re eating no processed foods,” Lively explained in an Australian radio interview this week.

“[It] seems like, ‘Oh, that’s really easy to cut that out,’ but then you realize there’s soy in everything. Like, everything you eat, there is soy in it. Even if it’s healthy, Whole Foods-organic stuff, there’s always soy in it.”

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The former Gossip Girl still consumed sugar and sushi “in moderation” — even though rice in sushi is often heavily processed and can contain considerable amounts of sugar, which has been linked to obesity.

WATCH: Do you know how much sugar you’re eating?

Gluten-free foods can be quite processed as well, and one study found going gluten-free to lose weight may do more harm than good.

Lively’s nutritionist is the brain child behind the questionable diet, which we asked a couple dietary experts to weigh in on.

What health experts say

“I don’t think soy makes people gain weight simply because it’s soy,” obesity expert Yoni Freedhoff told Global News.

Edmonton-based registered dietitian Lalitha Taylor, who’s a self-confessed “huge fan of soy,” thinks many people are misinformed regarding the plant protein and its role in health.

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“Soy has numerous health benefits,” she explained.

It’s a rich source of calcium, iron, and fiber, according to the dietitian. Soy also contains all your essential amino acids (meaning it’s a “complete protein”). Taylor said a 3/4 cup of cooked soybeans contains as much protein as 1/2 a cup of cooked meat.

Taylor points out 15 to 20 grams of soy is consumed within an Asian diet.

“If there was a connection between soy and weight gain, I would think that we would see much higher rates of obesity within certain groups of Asians, such as the Japanese.”

But that’s not the case.

So why do some shy away from soy?

The issue seems to be with soy protein isolate, which is soy protein that’s been extracted from soybeans. Karen Ansel, an author and registered dietitian, told SELF it shows up in bread, cereal, soup, and energy bars.

READ MORE: The skinny on snack bars — What to look for on the nutrition label

“If you are constantly seeing the words ‘soy protein isolate’ on the ingredient lists of the foods you eat, it might be a wake-up call that you’re eating too many processed foods, which can pack on the pounds,” Ansel said.

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The problem, thus, seems to be less with soy protein isolate and more with processed foods, which it’s always a good idea to steer clear from as they’re often loaded with sugar and salt.

Less processed soy foods include tofu, edamame or soy beans, and soy milk.

Aside from the misguided belief soy can cause weight-gain, people may avoid it for two other reasons. Some claim it’s an “estrogenic,” meaning it can increase the amount of estrogen hormone in your body. Others worry about it being genetically modified.

Freedhoff isn’t concerned about either.

“Though there are phytoestrogens in soy, I’m not aware of any robust studies demonstrating risk,” he said. “[As for GMOs]… as far as consumption goes, they’re totally safe.”

Those who do worry can always look for GMO-free versions of their favourite soy product.

Taylor adds research has shown two to three servings of soy per day can prevent breast cancer (this doesn’t pertain to soy supplements). And two servings of it per day is safe for breast cancer survivors.

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Daily consumption can also help reduce one’s risk of cardiovascular disease, she says, and alleviate symptoms of menopause.

So feel free to have that soy latte without fear that it’ll wreak havoc on your waistline.

And remember: moderation is key and all foods can affect people differently.

READ MORE: Top 6 weight loss mistakes, according to diet and exercise experts

In Lively’s case, her rigorous trainer-led workouts (which she estimated to be “13-hours” long) five to six times a week likely had a lot to do with her body transformation.

Breastfeeding, which she was doing at the time, probably helped too.

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