Hilary Duff recently admitted she's a fan and follower of Gwyneth Paltrow's "starvation diet."
Paltrow, 50, made headlines earlier this year when she revealed controversial wellness tips, which included intermittent fasting followed by bone broth meals.
"I know Gwyneth is in trouble for saying this, but sometimes I try to just drink coffee in the morning and starve off my hunger," Duff said during an interview on Molly Sims' "Lipstick on the Rim" podcast.
The "How I Met Your Father" actress isn't the only Hollywood star to go to extremes and maintain a strict routine. Ashton Kutcher once ate nothing but fruit to get into character for a role, while Tom Brady is known to stay away from nightshades – flowering plants (think tomatoes and strawberries) which may cause inflammatory issues.
Jenn Zerling, nutrition counselor, author and CEO of JZ Fitness, told Fox News Digital that trendy diets could have a negative impact on both mental and physical health.
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"Fad diets are very short-lived and provide for an emotional rollercoaster," she said. "For some, it causes eating disorders and poor body image. In the thousands of cases I've managed, people have tried every diet under the sun and everyone wants something that will allow them to eat the foods they enjoy, while losing weight and feeling great. This is possible when people open up to learn about their body "
Hilary Duff revealed that food is on her mind from the moment her feet hit the floor in the morning.
"I wake up really hungry," the mother-of-three said. "I'm obsessed with those cauliflower rounds. They're super clean."
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Duff prepares the cauliflower in an air fryer, then tops her veggie with "egg salad." She offered up other choices including "avocado, or I'll put like a fried egg and like a vegan sausage. I do overnight oats."
Hilary also said during the interview that she does "a lot of cardio. I love to hike. I'm playing tons of tennis right now." She admitted her fear of getting "too bulky," and added, "I would love to have the skinniest little pencil arms."
The former Disney star has previously discussed her "horrifying" eating disorder from when she was a teenager working on the Disney Channel's "Lizzie McGuire." At one point she said she weighed 98 pounds and was "totally obsessed with everything" she ate.
"I was way too skinny. Not cute," Duff told Women's Health Australia. "And my body wasn’t that healthy — my hands would cramp up a lot because I wasn’t getting the nutrition I needed."
In March, Paltrow shared insight into her eating habits on an episode of "The Art of Being Well."
"I do a nice intermittent fast," she said. "I usually eat something about 12. And in the morning, I’ll have some things that won’t spike my blood sugar. So, I have coffee, but I really like soup for lunch. I have bone broth for lunch a lot of the days."
Zerling, who also coaches at Orangetheory Fitness, explained that Hilary and Gwyneth's caffeine-only morning routine isn't the worst plan, but can have a few negative side effects.
"There is no known detriment to consuming coffee first thing in the morning and most likely these ladies do so without anything in it to prolong their intermittent fast.," she said. "The only detriment is some folks may be slow metabolizers of caffeine and this can lead to insomnia, increased anxiety, and potentially fast blood sugar drops."
She added, "If an individual works out on caffeine first thing in the morning, they can also experience heart arrhythmia, an increase in blood pressure and potentially heartburn."
"It's important to note that relying solely on caffeine to stave off hunger may not be the healthiest approach in the long run," Zerling continued. "Caffeine can affect individuals differently, and excessive consumption may lead to side effects such as jitteriness, anxiety, disrupted sleep, or an increased heart rate. Moreover, using caffeine to suppress appetite could potentially interfere with adequate nutrient intake and disrupt a balanced diet."
When Ashton Kutcher attempted an extreme fruit diet to prepare for the role of Steve Jobs in the late Apple founder's 2015 biopic, he landed in the hospital.
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Kutcher's wife, Mila Kunis, confirmed the wild fruitarian diet was "so dumb" while chatting on the YouTube show "Hot Ones."
Ashton mimicked Jobs' carrot juice intake to make his skin look orange, which gave him such horrible back pain that he needed medical attention.
"He also, I think, only ate like grapes at one point?" Kunis said. "We ended up in the hospital twice, with pancreatitis."
Zerling said eating only pure fruit can be "a death wish" for some people already suffering from pre-existing conditions such as diabetes or obesity.
"While fruits are lower in calories and can cause weight loss for some in the short run, the body is denied vital macronutrition for everyday functioning," she said. "This diet provides no essential fatty acids which are important for your nervous system, hormones, nutrient transport through the body and insulation of every cell in the body."
Oprah Winfrey once eliminated all "white foods" from her daily intake, and saw quick results on the scale.
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At the time, the former talk show host said she "cut out white rice, white pasta and white breads," which resulted in an almost immediate 10-pound weight loss.
"There are huge benefits to eliminating the white carbohydrates from the diet as listed by Oprah," Zerling said. "There is no nutritional benefit to any of those processed carbs."
"Eliminating carbohydrates from a diet, as Oprah Winfrey mentioned with regard to ‘white foods’ like breads, pastas, and rice, is known as a low-carbohydrate or very low-carbohydrate diet," she said. "This approach can be beneficial for weight management, as it may lead to weight loss by utilizing stored fat as a fuel source and reducing appetite. It can also help stabilize blood sugar levels, making it advantageous for individuals with conditions like diabetes."
"Additionally, low-carbohydrate diets have shown positive effects on markers of metabolic health, such as blood pressure and cholesterol levels," she explained. "However, completely eliminating carbohydrates may lead to nutrient deficiencies and make it challenging to sustain a balanced and varied diet in the long term. It can also potentially impact athletic performance, as carbohydrates are an important source of energy for high-intensity physical activities."
When celebrity trainer Tracy Anderson created the baby food diet, Jennifer Aniston was reportedly one of her clients to jump on the bandwagon.
The "Friends" star allegedly dropped 7 pounds in one week by eating 14 portions of purées formulated by Anderson, who claimed the trend was more of a "liquid cleanse" and "body boost."
"There is no benefit to blending your food to lose weight," Zerling said. "Most of these baby foods remove the fiber in the food to allow for easy absorption in an underdeveloped gastrointestinal tract, such as for babies."
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She added, "The only reason why Jennifer Aniston lost weight on this ideology is because the calories were most likely less than 500 for the whole day. Can you imagine having a resting metabolic rate of 1300 calories and not feeding your body with at least what you burn to run your heart, brain and other autonomic systems?"
For the most part, Tom Brady's rigorous health habits seem the most balanced. His self-titled T12 routine includes a diet comprised of 80% organic fruits, vegetables, nuts, seeds and whole grains, and the other 20% grass-fed organic meat and hormone- and antibiotic-free poultry.
The former NFL quarterback also stays away from nightshades, including peppers, potatoes, tomatoes and eggplants.
"One thing of note is an athlete like Tom Brady most likely has a high resting metabolic rate (how many calories he burns at rest) to where he can afford more carbohydrates than the average person," Zerling said. "If he is maintaining an active lifestyle as he did when he was a professional athlete, he can consume grains and fruits in higher amounts compared to the average person."
"The 80/20 ratio of plant-based to animal-based foods in the TB12 Method, it aligns with recommendations for a predominantly plant-based diet, which has been associated with numerous health benefits," she said. "However, the specific requirement for grass-fed, organic meats and hormone- and antibiotic-free poultry may limit options and increase the cost of the diet."
Zerling noted her personal "JZ Fitness" five anchors promote optimal health: nutrition, hydration, fitness, sleep and personal management.
"All five anchors are equally important, and when all five anchors are practiced each day, people not only feel great, but they feel emotionally and mentally committed to the journey of optimal aging," she said.
"The bonus – they achieve their goal weight without even trying.
