The effectiveness of cardio for fat loss is often overstated, as research suggests its impact may be less significant than commonly believed. While cardio is beneficial for heart health and overall well-being, it doesn't lead to a proportional fat loss based on calorie expenditure alone. A 2016 study by Herman Ponzer introduced the constrained energy model, which posits that as individuals engage in more cardio, their bodies respond by conserving energy, thereby reducing overall calorie burn throughout the day. This compensation can manifest through reduced daily movement or subconscious behavior changes, and some people may also eat more after cardio sessions, negating the calorie deficit achieved. Research shows that those who add cardio without modifying their diet tend to lose only 20 to 50 percent of the expected weight loss from the calories burned. A study led by Daniel Plotkin compared various types of cardio, including high-intensity interval training (HIIT) and moderate-intensity exercises, and found no significant difference in fat loss outcomes between them, with both showing minimal effects. The results indicated that neither high-intensity nor low to moderate-intensity cardio had a noteworthy impact on fat loss, revealing that the anticipated benefits might be more illusory than real.