Below is a breakdown of common reasons you might not see the weight loss progress you once were.

1. Plateauing Metabolism: As the body loses weight, it adjusts to the new lower weight by slowing its metabolism. This means the body burns fewer calories at rest, making it harder to lose weight.
2. Loss of muscle mass: When weight is lost, the body often loses muscle mass, which contributes to a slower metabolism.
3. Hormonal imbalances: As weight is lost, hormone levels in the body may change, making it harder for the body to burn fat.
4. Adaptation to diet and exercise: As the body becomes accustomed to the diet and exercise routine, it becomes harder to continue making progress.
5. Lack of variety in diet: Eating the same foods can make the body less responsive to weight loss.
6. Not enough sleep: Lack of sleep can also cause weight loss to slow down. Make sure you’re getting seven to eight hours every night for optimal. 
7. Stress: High levels of stress can cause weight loss to slow down and can even result in weight gain.
8. Not tracking progress: It can make it difficult to identify why weight loss has slowed down.
   

Another critical factor is age. As we age, our bodies undergo natural changes that can make weight loss more challenging. Some of the ways that age can affect weight loss include:

1. Metabolism slows down: As we age, our metabolism slows down, which means that we burn fewer calories at rest. This can make it harder to lose weight.
2. Hormonal changes: With age, our hormone levels change, which can make it harder to lose weight. For example, our growth hormone and testosterone levels decrease as we age, making it harder to build muscle and maintain a healthy metabolism.
3. Loss of muscle mass: We naturally lose muscle mass as we age, making it harder to lose weight. This is because muscle mass is more metabolically active than fat, so a loss of muscle mass can lead to a slower metabolism.
4. Decreased physical activity: As we advance in age, we may become less active, making it harder to lose weight.
5. Medications: We may be more likely to take medications that can cause weight gain.
6. Health conditions: As we age, we may be more likely to develop health conditions that can make it harder to lose weight, such as diabetes or heart disease.

Despite these challenges, losing weight and maintaining a healthy weight at any age is still possible. 

Focusing on healthy lifestyle choices such as eating a balanced diet, engaging in regular physical activity, and getting enough sleep is essential. 

Working with a healthcare professional or personal trainer is also necessary to develop a personalized weight loss plan that considers any health conditions or medications that may affect weight loss.