In the world of fitness and weight loss, we are often told that variety is the spice of life and that a flexible diet is the only way to succeed. However, fitness expert Jeremy Ethier recently showcased a different approach that seems to fly in the face of traditional dieting wisdom. The “CPB Diet” (Chicken, Potatoes, Broccoli) is an intentionally “boring” eating plan designed to maximize fat loss by simplifying food choices to the extreme.,. While it sounds monotonous, the results from a 30-day experiment involving two fit individuals were nothing short of scientific breakthroughs.,.
The Experiment and the Subjects
To test the effectiveness of this diet, Jeremy recruited two subjects who were already in decent shape but wanted to lose stubborn fat. Max, a personal trainer and train conductor, started the challenge with 19% body fat.. Despite his solid workout routine, Max struggled with “binge-like” eating habits, often visiting buffets and eating until he felt physically ill, which negatively impacted his sleep..
The second subject, Isabelle, a coach, began with 31% body fat.. While her body fat was better than the national average, she struggled with the time-consuming nature of traditional dieting, such as weighing food and tracking every single calorie.,. The goal for both was to see if a hyper-simplified diet could reset their habits and destroy body fat without the need for constant calorie counting..
The Three Golden Rules of the CPB Diet
The CPB Diet is built on simplicity. There are only three main rules that participants must follow for 30 days:
-
Limited Food Choices: You can only eat chicken breast, potatoes, broccoli, and carrots.. The catch is that you can eat as much of these foods as you want—essentially an “all-you-can-eat” buffet of these specific items..
-
Controlled Fats: Participants are allowed one tablespoon of olive oil per meal for cooking or flavoring..
-
Zero Liquid Calories: There are no sodas, fruit juices, or even artificial sweeteners allowed..
The theory behind this extreme restriction is to provide a “short reset” for the brain.. By removing the pleasure-seeking aspect of food, the body stops chasing “hits” of dopamine from sugar and variety, and begins to recognize true hunger signals again.,.
The Science of “Boredom” and Fullness
You might wonder why these specific foods were chosen. Jeremy explains that they were scientifically selected to maximize three things: fullness, calorie burn, and habit rewiring..
1. The Satiety King: Potatoes
Most people think of potatoes as “fattening” carbs, but science says otherwise. In a famous 1995 study, researchers compared 38 different foods to see which kept people full the longest. Boiled potatoes crushed the competition, ranking three times more filling than white bread and eight times more filling than croissants.,. However, preparation matters; if you fry them into chips or fries, this satiety benefit disappears..
2. The Reward System Reset
When we eat a variety of tasty foods, our brain’s reward system lights up.. This is why even after a full meal, we often have “room for dessert”—it is called sensory-specific satiety.. By eating the same simple foods every day, the reward system isn’t triggered, and people naturally end up eating 20% to 30% fewer calories without even trying.. One study showed that people eating the same meal daily naturally reduced their intake by 100 calories per meal by the end of a week simply because the food became less “exciting.”.
3. High Volume, Low Calorie
Chicken breast provides lean protein, while broccoli and carrots provide fiber. These foods add “volume” to the stomach, making you feel physically full while consuming very few calories.. Additionally, protein and fiber take more energy for the body to digest, meaning you actually burn more calories just by processing these foods..
Week One: The Mental Battle
The first week was the most difficult for both Max and Isabelle. The psychological shock of “chicken for breakfast” was a major hurdle.,. Isabelle noted that she felt “trapped” by the lack of variety, while Max was plagued by constant images of potatoes popping into his head whenever he felt hungry.,.
However, by the end of the first week, something interesting happened. Despite being allowed to eat as much as they wanted, neither felt hungry.. In fact, they struggled to eat enough food.. Jeremy’s app estimated that Max was only eating about 1,800 calories a day, and Isabelle was around 1,300 calories, yet both reported having high energy and mental clarity.,. Physically, the results were immediate: Max lost 5 pounds in the first week, and Isabelle saw her waist measurement drop by 1.5 cm..
The Pivot: Flexibility vs. Strictness
After the first week, Jeremy introduced a choice. To make the diet more sustainable, he offered them the chance to add more variety. Isabelle chose to add eggs to her breakfast, while Max, surprisingly, decided to stay 100% strict on the original CPB plan.,.
As the weeks progressed, Isabelle’s diet became a “CPB Flex” version. She eventually added:
-
Greek yogurt and protein powder for variety in protein..
-
Oranges and avocados (limited to half an avocado to replace the olive oil)..
-
Bok choy and tomatoes for extra nutrients.,.
Jeremy also introduced a “treat meal” once a week for Isabelle—a concept known as a “planned hedonic deviation.”. Research suggests that these temporary breaks can actually improve long-term results by keeping social lives intact and providing a mental boost..
Overcoming Social Challenges and “FOMO”
One of the hardest parts of any strict diet is the social cost. Because this experiment took place during the holidays, both participants faced a lot of “FOMO” (fear of missing out).. Max had to skip family lunches and potlucks because he didn’t want to sit and watch others eat food he couldn’t have..
To cope, Max replaced his eating habits with new, healthy activities.. Instead of going out to eat, he began drinking tea, reading books, and planning social gatherings that didn’t revolve around food.. This is a major benefit of the diet: by removing the hundreds of daily decisions we make about food (where to eat, what to order, how much to have), you save mental energy for more important things like work and exercise..
The Final Stretch and Physical Toll
While the results were fast, the strictness did take a toll. Max eventually hit a breaking point near the end of the 30 days.. He felt irritable and began to worry if he was losing muscle because he was getting smaller so quickly.. He even described “spiraling down a deep hole” of doubt while lying on a gym mat..
Isabelle also faced challenges, specifically dealing with her menstrual cycle, which can ramp up hunger and cravings.. Rather than changing the whole plan, she managed this by increasing her meal volume with more potatoes and using tea or gum to handle cravings..
The Shocking Final Results
At the end of the 30 days, both participants underwent DEXA scans to measure their exact fat loss and muscle retention. The results were staggering:
-
Isabelle’s Results: She lost 5 lbs of pure fat and dropped her body fat from 31% to 28%.. Most impressively, she actually gained half a pound of muscle during the process.. Jeremy noted that a 3% drop in body fat for a woman in one month is an exceptionally large change..
-
Max’s Results: His results were described as a “breakthrough in science.”. Max lost 14 lbs of fat in just 30 days.. His body fat plummeted from 19.3% down to 12.9%.. Despite the rapid weight loss, the scan showed that he maintained all of his muscle mass, likely because his protein intake remained very high and he continued training hard..
Key Takeaways for the Average Person
While Jeremy doesn’t necessarily recommend that everyone follow such an extreme diet forever, this experiment proves several key principles that anyone can use:
-
Simplicity Wins: Reducing the number of decisions you make about food can prevent “decision fatigue” and help you stick to your goals..
-
Prioritize Satiety: If you struggle with hunger, base your meals around high-satiety foods like boiled potatoes and lean protein.,.
-
The “Boredom” Effect is Real: If you find yourself overeating, it might be because your diet has too much variety, constantly triggering your brain’s reward system..
-
Short-Term Resets Work: A 30-day “boring” phase can help psychologically reset your relationship with food, making it easier to transition into a more flexible, sustainable plan later.,.
-
Final Thoughts
The CPB Diet proves that fat loss doesn’t have to be complicated. You don’t need fancy meals or strict calorie counting.
Sometimes, a simple and repetitive diet can give powerful results.
Whether you follow it strictly or add some flexibility, keeping your meals simple may be the key to losing stubborn body fat.