The antonyms for the phrase "get into shape" are varied and include words such as deteriorate, weaken, decline, and deteriorate. These words indicate loss of fitness, strength, or health. Neglecting a healthy lifestyle can lead to deterioration of the body, causing it to weaken and decline. Adverse health effects like weight gain, loss of flexibility, reduced cardiovascular fitness, and decreased lung capacity are common results of neglecting exercise and a balanced diet. Therefore, it is important to incorporate regular exercise, dietary modifications, and lifestyle changes to maintain good health and fitness. Staying active and consuming a healthy diet can help prevent adverse health effects and increase longevity.