Weight fluctuates throughout the day for many reasons, with diet being a primary factor. The balance between energy consumed from food and energy expended through physical activity determines whether you gain or lose weight. When your calorie intake exceeds the calories burned, weight will increase, sometimes rapidly.

Generally, the most consistent weight measurement is taken in the morning after waking up and before consuming any food or drink. As the day progresses, your weight tends to change due to the impact of larger meals or exercise. After a workout, weight may temporarily decrease due to fluid loss through sweat. Some athletes can lose 6-10% of their body weight after a training session. For most people, a decrease of one to two kg after exercise is common.

Another reason for weight fluctuations is excessive water intake. One liter of water weighs almost 0,9 kg, so drinking a large amount of water in a short period can temporarily increase your weight. However, this does not mean you should limit water consumption. In the long term, adequate hydration, especially by replacing sugary drinks with plain water, can support weight management.

Conversely, dehydration can also cause rapid weight loss. Weight changes also depend on bowel movements and urination. Eating a lot but not yet having a bowel movement will increase weight, sometimes referred to as "fecal weight". Drinking plenty of water without urinating has a similar effect. Diarrhea, on the other hand, can lead to dehydration and weight loss in some individuals.

Furthermore, after nights of insufficient sleep, you tend to feel hungrier, eat more, and are more prone to weight gain by the end of the day. Note that weight results also change if the weighing conditions are inconsistent. The surface where the scale is placed needs to be flat and firm, your posture when standing on the scale should distribute weight evenly across both feet, and the clothes worn during weighing should be similar. Even minor differences can cause significant discrepancies in your weight measurement. Additionally, not all scales provide the same results.

Overall, daily weight fluctuations are normal. Therefore, there is no need to worry excessively about small variations. Regularly monitoring your weight can help you understand these fluctuations and maintain a healthy weight.

Doctor Nguyen Hoai Thu

Vietnam Institute of Applied Medicine