How Does a Reverse Diet Work? Description, Drawbacks, and Advantages

A reverse diet is a method of eating that aims to gradually increase calorie intake over several weeks or months until it reaches levels that meet energy demands. The main goal of this approach is to accelerate the metabolic process and avoid excessive weight gain. Originally, this strategy was used by bodybuilders during the competition preparation phase when they adhered to strict dietary restrictions. It was observed that after participating in competitions and returning to a normal diet, their body weight increased significantly, even though the calorie intake was not that high. One of the observed side effects is the increased amount of water in the body, which leads to weight gain. However, it turns out that this is not the only reason for the rapid yo-yo effect.

Research shows that during the long-term implementation of a negative calorie balance, many changes occur in the body, including changes in the concentration of hormones. Long-term calorie reduction can lead to a decrease in leptin (also known as the satiety hormone), insulin, testosterone, and thyroid hormones. Insulin, alongside leptin, signals the feeling of fullness but is also responsible for the metabolism of macronutrients and the inhibition of muscle tissue breakdown (K. Strohacker et al. 2013). Testosterone, in turn, is considered to be a major inhibitor of adipogenesis (the process of forming fat cells), so its proper level in the body reduces the fat mass of the body. Thyroid hormones play an important role in maintaining the correct body weight, as they are involved in the regulation of the speed of metabolism and thermogenesis. In case of a deficiency of these hormones, the speed of metabolism decreases, leading to a reduction in the basal metabolic rate and a decrease in the body's energy requirements (R. Mullur, Y. Liu, G. A. Brent 2014). In contrast to the above-mentioned hormones, during weight loss, the level of cortisol (the stress hormone) and ghrelin (the hunger hormone) increases, leading to an increase in appetite (L. M. Rossow et al. 2013).

The number of kilocalories that the body needs to function and perform the various functions of daily life depends on a number of factors. First of all, they are body mass, age, and growth. It is affected by 3 main factors: basic metabolism, thermogenesis of fat, and physical activity. The basic metabolic rate (PPM), or the amount of energy needed to perform the basic functions of life, depends on many factors, such as body weight, age, growth, health and nutrition, level of hormones, intake of medications, and the activity of muscle tissue in the body. CPM is also influenced by thermogenesis popołkowa, the amount of energy needed for the digestion and absorption of food, which accounts for about 10% of the PPM. Finally, physical activity, which can be divided into training and non-training (non-exercise activity thermogenesis or NEAT), also affects the CPM. During weight loss, introducing different types of training allows for the burning of additional kilocalories, but limiting non-training activity can lead to a decrease in CPM (H. Ciborowska, A. Rudnicka 2014, G. R. Hunter et al. 2015).

A series of changes that occur during the weight loss process can actually lead to an increase in body weight after the completion of weight loss. In order to prevent this, it is increasingly recommended to introduce a reverse diet, which allows the body to gradually adapt to a larger amount of energy provided by slowly regulating hormone levels and facilitating an increase in post-workout activity. It is recommended to add 50-100 kilocalories per week for 4-10 weeks to achieve total metabolism. In addition to increasing the amount of nutrition in the diet, the number of cardio workouts per week can also be reduced (provided they were performed). Gradually lifting energy restrictions can protect against binge eating, as the thought of the end of the diet and the allowance to eat everything previously considered forbidden does not arise. According to the proponents of the reverse diet, it leads to greater flexibility in nutrition, so that one can allow oneself small exceptions more often without serious consequences. When increasing the calorie content in the menu, the risk of deficiencies is also reduced and the amount of energy is increased. Severe restrictive diets are often accompanied by a worse mood, fatigue and concentration problems, which improve after the introduction of a larger amount of nutrients.

Unfortunately, there is a very limited number of studies available on reverse diets. However, it is known that the body adapts to more calories just as well as it does to reducing them. The changes in metabolism that occur during reduction are relatively quickly returning to the pre-weight loss state, regardless of whether the reverse diet is applied or not (E. Fothergill et al. 2016). However, the major disadvantage of reverse diets is the need to count calories and weigh products to ensure that the amount of added energy is not too much. This method can lead to a deterioration of the relationship with food and the appearance of obsessive thoughts about it (C. C. Simpson, S. E. Mazzeo 2017). Additional calories should primarily come from carbohydrates and fats, but their specific sources are unfortunately rarely given, which can lead to a more frequent selection of highly processed products. However, the most important thing is that the person applying the reverse diet is still in an energy deficit and thus prolongs all the negative consequences that come with the reduction process. Indeed, their severity decreases with each week, but the deficit is still a significant burden on the body, which can lead to the development of many diseases and disorders in the long term, such as anemia, reduced immunity, weakened skin, hair and nail condition, digestive problems or osteoporosis. Interestingly, research indicates that people with a higher metabolic rate tend to gain slightly more weight than those with a lower PPM, which shows that the assumptions of the reverse diet may not be entirely correct (R. Rimbach et al. 2022).

The reverse diet, where caloric intake is gradually increased, is gaining popularity among individuals who engage in regular physical activity, as well as those who have had no luck in weight loss attempts or frequently experience the yo-yo effect. However, this method is not ideal for everyone.

Besides hormonal changes, decreased total metabolism, and reduced spontaneous post-workout activity, the main cause of weight regain is the approach to nutrition. Unfortunately, many individuals seeking weight loss divide their lives into two stages: the diet phase and post-diet phase. Once they reach their desired weight, they return to their previous dietary habits and completely abandon developed healthy habits, believing they no longer need to limit themselves, leading to the rapid yo-yo effect. Reverse diet slightly extends the period of applying healthier eating habits but does not contribute to their long-term reinforcement. Therefore, the key to maintaining proper body weight is building a healthy lifestyle, i.e., introducing a balanced diet and physical activity that can be sustained long-term. A minor energy deficit will undoubtedly not lead to significant hormonal and metabolic changes in the body, and as a result, consuming the number of kilocalories consistent with the total energy expenditure will not result in a yo-yo effect.

Despite the idea of a reverse diet appearing to be the optimal solution for its advocates to exit a calorie deficit and maintain a low body weight, it is in reality merely another dietary approach that lacks scientific validation. This diet simply prolongs the period of energy deficiency, which constitutes a direct burden on the body. The most effective method to preserve a lean physique following weight loss is to foster healthy eating habits, heed the signals sent by one's own body, respond to sensations of hunger and satiety, and attend to other facets of a healthy lifestyle, such as sufficient sleep, consistent physical activity, and positive mental health.