The aim of this paper was to point out the importance of high protein intake and strength training for achieving successful results with a calorie-restricted diet. An increasing number of people are dealing with the problem of excessive body weight, i.e. they want to get rid of excessive subcutaneous fat. In order to lose body weight, it is necessary that the total daily energy expenditure is higher than the daily energy intake (calories from food). With fat loss as the primary goal, the secondary goal should be to maintain muscle mass. However, few are the ones who achieve optimal results (losing fat while retaining muscle) and even rarer are those who are able to sustain them for a longer time period. There are two important factors that need to be manipulated for maximal muscle mass retention. Strength training is the first factor that plays an important role in building muscle and retaining its volume. Namely, in order for the muscle to increase its size, a mechanical stimulus is required. Moreover, due to the principle of adaptation, it is necessary to continuously increase that stimulus. The other factor relates to adequate nutrition. Since protein is required to build muscle, emphasis should be placed on its quality and quantity in a diet. Firstly, it is necessary to reduce calorie intake (achieve a calorie deficit) and then ingest enough quality protein to support muscle growth and/or its volume. By implementing the two aforementioned factors, it is possible to optimize the results of a calorie-restricted diet in recreational lifters.