Salt is a condiment that has been demonized since the early 1900s (1).

High salt diets are often linked to health conditions like high blood pressure and stroke, and occasionally, some of my nutrition clients believe their weight gain may be due to the high salt meal they had for dinner the night before.

But would salt, as part of an otherwise healthy diet, truly cause you to gain body fat?

This article explores the link between salt and weight gain.

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Research suggests that people who eat a salt-rich diet often weigh more. They also have a higher body mass index (BMI), larger waist circumference, and higher waist-to-height ratio than those who eat less salt (2).

It’s easy to assume, then, that a salt-rich diet promotes weight gain. Yet, there may be a few alternative explanations for these correlations.

Salty foods, hunger, and appetite

Studies have found that the people who eat the most salt often also eat the largest amounts of food and the most calories per day (2).

Diets that are rich in sugar-sweetened beverages and ultra-processed foods tend to contain more salt than minimally processed ones (2, 3, 4, 5).

Ultra-processed foods satiate your hunger less effectively. As a result, they may cause you to unwittingly eat more calories than your body truly needs (2, 3).

In this case, the amount of salt in a person’s diet can be seen as an indicator of diet quality. In turn, a poor quality diet rich in ultra-processed foods — rather than its salt content, specifically — is the likelier cause of weight gain.

Salt may increase water weight

Salt is rich in sodium, a nutrient we all need — albeit in much smaller amounts than most of us currently consume.

Your body is designed to tightly regulate its sodium concentration.

Eating salty foods causes your body’s sodium concentration to rise. To counteract this, your body’s natural response is to increase your thirst while reducing your urine output.

It then holds onto as much water as it can to dilute its sodium concentration back down to its preferred level (6).

Studies suggest that this water retention may cause up to a 2.2-pound (1-kg) difference on the scale (7, 8, 9).

So my clients worrying that last night’s salty meal caused them to weigh more the next morning weren’t totally wrong.

However, when equal in calories, saltier diets don’t seem to cause you to gain more body fat than lower salt ones. Therefore, any extra weight on the scale may purely be water weight (8).

Salt won’t directly increase your body fat

Some studies suggest that salt may cause you to gain body fat as well, independently of the number of calories you eat (10, 11, 12).

Research in mice further suggests that a high salt diet may make the body resistant to leptin — a hormone responsible for preventing hunger and helping you feel full and satisfied (13).

The assumption is that leptin-resistant mice would eat more and therefore gain weight. Some researchers suggest that high salt diets may affect humans in the same way, although this theory has yet to be tested.

Importantly, the studies suggesting that salt may cause weight gain regardless of your calorie intake used self-reported dietary records, which are notorious for their inaccuracy, to estimate what people ate (14).

When researchers controlled the number of calories participants ate by providing all meals to them, they observed different results.

Those eating a lower salt diet lost more water weight than those eating higher amounts of salt. However, there was no difference in body fat changes between those on the lower or higher salt diet (8).

So again, salt may cause you to hold on to water, but it’s unlikely to cause you to gain body fat.

If you’d like to lose body fat, try focusing on sustainable changes you can make to your diet that will naturally reduce your calorie intake.

Summary

A high salt diet may indirectly affect weight gain. Although salt may cause you to retain water, it’s unlikely to cause you to gain body fat. To lose body fat, find sustainable ways to reduce the total number of calories you eat.

Salt may temporarily increase your body weight by causing you to retain water.

Salt-rich diets may also indirectly cause you to gain weight because they often contain large amounts of ultra-processed foods.

Highly processed foods are less satiating, which can ultimately cause you to eat more calories and gain weight.

However, when equal in calories, a high salt diet won’t cause you to gain or lose more body fat than a lower salt one.

If you want to lose body fat, switch the focus from the salt content of your meals toward the sustainable changes you can make to reduce the number of calories you eat.