Here's the Diet That Jessica Simpson Followed to Lose 100 Pounds—but Is It Healthy?

Jessica Simpson has been honest about everything from her career ups and downs to her sobriety journey and her relationship with something very close to home—in fact, it is her home: her body.

In April, The 41-year-old singer, actor, entrepreneur and mom of three took to Instagram to share a radiant, smile-filled photo to celebrate a major milestone: "I have gained and lost 100lbs 3x so I never thought this moment could or would happen, but I'm finally spring breakin' wearin' a BIKINI!!!!!!"

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She's not alone in terms of the weight-loss roller coaster, says Mary Stewart, RD, LD, a registered dietitian and the founder of Cultivate Nutrition in Dallas. In fact, it has a name: weight cycling. "Weight cycling is defined as repeated attempts at losing and gaining weight. Some studies show the role weight cycling may play in adverse health events," she says, including higher risk of death, poor sleep quality and symptoms of depression. It's reported that 20% to 35% of men and 20% to 55% of women have cycled up and down in their weight, according to data published in the Journal of Obesity & Metabolic Syndrome.

So, why might someone lose and then regain the weight (and more)? "One of the biggest reasons yo-yo dieting is a struggle for so many is because the dietary approach is not sustainable for that individual's lifestyle," Stewart says. "Unfortunately, many trendy diets create unnecessary drastic and strict dietary changes, which are not feasible to maintain, and therefore these diets are not designed in a way that leads to true habit change," she adds.

As for Simpson, after welcoming her youngest child, Birdie Mae, in March 2019, the star embarked on a program designed by celebrity trainer Harley Pasternak.

The plan in particular: The Body Reset Diet, which is described in detail in a recently revised book. In 2019, Pasternak told People: "I've kind of helped her come back after each baby, and this is a bit different, in that she said she was tipping the scales at 240 [post-delivery]. This is sort of the aggregate of being pregnant nonstop for a decade, and so we had a little more of a challenge between this and the other ones." He adds to E News: "It had to be more than just getting back from her baby weight, but how do I keep whatever I am doing now forever. That's why we are not a big fan of doing any extreme diet or radical forms of exercise."

While she no longer relies on scales to judge her progress, Simpson has clearly maintained that post-baby loss for years and says that she feels physically and mentally stronger than ever.

So what is this "reset," exactly, and how did it help the fit mom change her life once and for all? We asked Stewart and Michelle Hyman, RD, a registered dietitian specializing in weight management in Long Beach, New York, for the scoop.

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Pasternak prescribed The Body Reset Diet to Simpson after the arrival of Birdie Mae. The program includes a focus on nutrition, exercise and lifestyle habits, including:

• Walking. Simpson started at 6,000 steps per day, then gradually worked up to 14,000 per day, according to E News.
• Trainer sessions. She fits in even more activity via 45-minute strength sessions three days per week with Pasternak and trainer Sydney Liebes.
• A technology "diet." To promote better sleep, Pasternak advised her to unplug from her devices for at least one waking hour every day.
• Quality sleep. Speaking of those zzz's, Simpson shoots for seven hours of shut-eye each night.
• Five "fueling occasions" each day. The Body Reset Diet includes three meals featuring protein, fiber and fat, as well as two snacks, such as almonds or edamame, per day. In the early phases of this diet, things are pretty strict (more on this shortly). Later on, food choices loosen up a bit. "... If she has a birthday party one night and a date night another night, she's going to indulge both of those nights, but that's it," Pasternak tells People. "It's about balancing in a way that doesn't make it painful or too much of a departure from your life before that."

In addition, Simpson also tossed out her scale and no longer weighs herself.

The official 15-day Body Reset Diet is split into three five-day phases:

• Phase 1: All meals are replaced by smoothies of different colors.
• Phase 2: Add in one solid food meal, such as a salad or sandwich.
• Phases 3 - 5: This begins the low-calorie, plant-based portion of the diet, designed to be followed for 15 days. Start by consuming two meals and one smoothie "meal." Alcohol is not allowed, nor are any meats. Dairy and eggs are A-OK.

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Not everyone will find this diet doable, particularly in how Phase 1 is extremely smoothie-heavy. "Consuming meals in liquid form is not necessary for weight loss. For many people, this may not be enjoyable or palatable," Hyman explains. "Smoothies, even when they contain fruits and vegetables, may not be as filling as solid meals. During the first two phases, the focus on smoothies can be difficult for individuals who enjoy eating shared meals with their loved ones at home or at restaurants," she says.

As for Stewart, she's a huge fan of smoothies. "They are a great way to pack in the nutrients in a convenient way. With that said, only drinking a smoothie for each meal, as referenced in the first phase of the diet, can be too challenging and encourage a caloric restriction that is too severe and unnecessary," she explains.

In later phases, if you choose your vegetarian meals and snacks wisely, you can fuel up in a well-balanced way, Hyman and Stewart agree, but that's a lot easier said than done. It can take a lot of planning to ensure each of your smoothies, meals and snacks offers enough protein, fat and carbs to provide enough energy.

Because the complexity of celebrity diets may not mesh with your own lifestyle, these are often short-term fixes. "Most people can follow diets or structured meal plans for short periods of time. These diets and meal plans that are glorified by celebrities are 'blanket' plans that are not individualized for the general public," Hyman warns. "The celebrity may be getting a personalized plan to their likes and dislikes due to paying large amounts of money for the service, but when they promote the plan in interviews, options generally aren't mentioned. Following a strict plan does not take into consideration everyday life, like social events involving food, vacations or eating at restaurants. It also does not address the underlying causes for unexplained weight gain; for example, struggling with self-care when stressed at work," she says.

The overall tenets are fairly sound, however, Stewart says, especially if you allow for more flexibility in the plan. "The combination of daily movement, consistent mealtimes, focusing on whole foods including a balance of fiber, healthy fats and lean protein, and prioritizing sleep will give the body the foundation it needs to maximize health," she says.

Just know that there's nothing magic about Simpson's specifics of meal and snacks, step counts and unplugged time. It's what works for you that matters. "According to research, there is actually no one optimal eating frequency for weight loss. Three meals and two snacks a day may work great for some, but not others," Hyman says.

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One smart move you can take from Simpson is ditching the scale. "I appreciate how she tries hard to not let a number on the scale define her. The number on the scale is just one way to measure health and certainly does not tell the whole story," says Stewart.

Should you try Jessica Simpson's diet? While there are benefits to the diet, including the focus on whole foods and consistent mealtimes, you do not need to follow the diet in order to lose weight or improve your health. In fact, you can lose weight and feel good with small changes, rather than entire lifestyle overhauls.

"When making any dietary or lifestyle change, it's about progress, not perfection, and making small, sustainable improvements. Once that particular change becomes a habit, you can build on it," Stewart says. For instance, you might replace a vending-machine snack with a smoothie this week, focus on sleep the next week and tack on 30 minutes of unplugged time the following.

For the best chance at finding a diet plan that's right for you and your lifestyle and gives you the optimal strategy for successful weight loss that you can maintain long-term, Hyman suggests consulting with a registered dietitian for individualized weight-loss advice.