# How Saunas Affect Weight Loss and Body Temperature

## a) How long would a 100 kg person have to spend in a sauna daily to lose 4 kg over 5 weeks?

- What are the key factors to consider in achieving this weight loss goal?

- How does the person's metabolic rate and calorie consumption play a role in weight loss?

- Why is it important to limit sauna sessions to 10-15 minutes?

- Are sauna sessions alone sufficient for safe and effective weight loss?

## b) Why do saunas generally recommend session limits of 10-15 minutes?

## c) How can we calculate a person's body temperature after spending the calculated duration in the sauna?

## a) Solution:

To lose 4 kg of mass, a 100 kg person would need to spend approximately 124 hours in the sauna over a period of 5 weeks, assuming the sauna sessions are solely responsible for the weight loss. This is not feasible or advisable due to safety concerns and potential negative effects on health.

## b) Answer:

Saunas generally recommend session limits of 10-15 minutes due to various reasons, including the risk of dehydration, overheating, and potential cardiovascular strain.

## c) Insight:

Calculating the person's body temperature after the calculated duration would require more specific information about the person's initial body temperature and environmental conditions. It is important to note that the body's heat transfer coefficient from air to the body surface is 12 W/(m²K).

To calculate the time required for weight loss, we need to determine the calorie deficit needed to lose 4 kg. One kilogram of body mass is roughly equivalent to a calorie deficit of 7700 kcal. Therefore, to lose 4 kg (4000 g), a person would need a calorie deficit of 31,000 kcal.

Assuming the sauna sessions are the sole contributor to the calorie deficit, we can calculate the calorie expenditure by multiplying the sweat rate by the duration of each session and the heat capacity of water. The person's sweat rate is 1 liter per hour, and the heat capacity of water is 4.18 J/(g°C).

Given that 9.3 g of fat releases 1 kcal of energy, we can convert the calorie deficit into grams of fat by multiplying it by 9.3 g/kcal. This gives us 288,300 g of fat that needs to be burned.

Using the person's metabolic rate of 2000 kcal/day and assuming all energy is derived from burning fat, we can determine the number of days required for weight loss. Dividing the total calorie deficit by the daily metabolic rate, we find that it would take approximately 155 days.

Converting this to weeks, we get approximately 22 weeks. However, this calculation assumes that the sauna sessions are the only factor contributing to weight loss and does not consider other important aspects such as diet and exercise.

Furthermore, spending such prolonged periods in a sauna can lead to dehydration, overheating, and potential strain on the cardiovascular system. Therefore, it is not feasible or advisable to rely solely on sauna sessions for weight loss.

Saunas generally recommend session limits of 10-15 minutes for several reasons. Prolonged exposure to high temperatures can lead to excessive sweating and dehydration, which can be dangerous. The risk of overheating and potential strain on the cardiovascular system increases with longer sauna sessions.

By adhering to shorter sessions, individuals can mitigate these risks and ensure a safer and more enjoyable sauna experience.

For part (c), calculating the person's body temperature after the calculated duration would require more specific information about the person's initial body temperature and environmental conditions. However, given the sauna temperature of 90°C, it is important to note that the body's heat transfer coefficient from air to the body surface is 12 W/(m²K).

This coefficient indicates the rate at which heat is exchanged between the body and the surrounding air. With this information, the body's temperature could be estimated using principles of heat transfer, but additional details are necessary for an accurate calculation.