The final weeks before summer vacation are often seen as an opportunity for a quick body “fix,” with the goal of achieving the so-called bikini body—a concept that continues to persist despite growing conversations around body positivity and embracing a healthy body at any size. In reality, however, this mindset often leads to drastic and unrealistic changes in both diet and exercise. Beyond increasing stress, these approaches can have important physiological consequences.
The outcome is not simply fat loss. Rapid weight-loss strategies can also compromise muscle function—the body’s ability to perform, recover, and maintain stable energy levels. This becomes particularly evident when the approach is aggressive, involving severe calorie restriction, excessive dietary limitations, inconsistent protein intake, and intense physical activity performed simultaneously.
What happens to muscle during severe calorie restriction?
Muscle tissue is far from static. It is constantly undergoing remodeling through a dynamic balance between muscle protein synthesis and muscle protein breakdown. When energy intake drops sharply, the body adapts by downregulating processes it considers energetically expensive, including the maintenance and renewal of muscle tissue.
Under these conditions, the risk of a negative nitrogen balance increases-a state in which protein breakdown exceeds protein synthesis. This does not necessarily mean a dramatic loss of muscle mass within a few days, but rather a gradual decline in muscle quality and function, resulting in reduced strength, lower endurance, and slower recovery.
Another important factor is that during periods of energy restriction, the body becomes less efficient at utilizing available amino acids for muscle repair and rebuilding. Even when dietary protein intake is adequate, an overall energy deficit limits the body’s ability to make optimal use of it.
Protein is about more than quantity
Adequate protein intake plays a fundamental role in preserving muscle function, particularly during weight loss. However, total protein intake is only part of the equation. Protein quality and how protein is distributed throughout the day are equally important.
For healthy adults whose energy requirements are met, a balanced diet -whether it includes animal-based foods or is entirely plant-based- is generally sufficient to provide adequate protein. However, during periods of increased physiological demand, such as menopause, older adulthood, regular exercise, or intentional weight loss, ensuring sufficient protein intake becomes even more important.
A well-planned plant-based diet can fully meet these increased requirements, but it requires more careful food selection and thoughtful combinations. This is because some plant protein sources provide lower amounts of essential amino acids -particularly leucine, the amino acid that plays a key role in stimulating muscle protein synthesis- per serving or per calorie than many animal-derived proteins.
In practice, the most effective strategy is not consuming a large amount of protein in a single meal, but distributing adequate protein evenly across the day. This provides muscles with repeated anabolic stimuli that support their maintenance, repair, and renewal.
How calories affect muscle health
One of the most overlooked factors affecting muscle function is overall energy availability. When calorie intake becomes excessively low, the body does not simply rely on stored fat for fuel; it also scales back essential processes involved in maintaining and repairing muscle tissue.
This can occur regardless of the dietary pattern someone follows whenever energy intake fails to meet physiological needs -whether because of severe calorie restriction, reduced appetite, or choosing low-energy-density foods without adequately replacing the missing calories.
Under these circumstances, a person may feel full while still consuming insufficient energy to support exercise performance, recovery, and normal muscle function. The consequences may include reduced endurance, poorer exercise performance and slower recovery after physical exertion.
Ultimately, muscle function is influenced not by a single factor, but by the combined effects of adequate energy intake, high-quality protein, and an appropriate distribution of nutrients throughout the day.
What to do before your vacation
If your goal is to have your vacation with a body that functions well -not simply one that weighs less- your priorities need to change. The first priority is consistency. Severe calorie restriction offers little long-term benefit when it comes at the expense of physical performance and muscle function.
The second priority is consuming enough protein and distributing it evenly throughout the day. For those following a plant-based diet, this means emphasizing a variety of protein-rich foods such as legumes, soy products, tofu, tempeh, whole grains, nuts, and seeds to ensure increased nutritional needs are met with ease.
The third priority is maintaining regular exercise, particularly resistance training or bodyweight exercises, to provide muscles with the stimulus they need to preserve strength and lean tissue.
Finally, it is equally important to let go of the “last chance” mentality. The body does not respond well to pressure, urgency, or crash dieting. Instead, it thrives on consistency, adequate nourishment, and sustainable habits.
From this perspective, the most effective goal is not aggressive weight loss but maintaining a body that functions optimally -supported by adequate energy availability and healthy muscle mass. After all, holidays do not require a body that has been pushed to change as quickly as possible. They require a body that can move, explore, stay active, and fully enjoy the experience without limitations.
True progress is reflected not only in appearance but in how you feel and perform every day -with energy, resilience, and a healthy, balanced relationship with both food and movement.
Resources
https://pmc.ncbi.nlm.nih.gov/articles/PMC3648712/
https://pmc.ncbi.nlm.nih.gov/articles/PMC8566416/
https://pmc.ncbi.nlm.nih.gov/articles/PMC6893534/
