When combined with fat, salt can override the normal ability of fat to promote a feeling of fullness, leading to passive overconsumption.
Weight gain is a complex issue but there is little doubt that the current food environment in Western countries – heavy in highly processed salty, sugary, and fatty foods – has had a big role to play.
Most of the salt in the diet has been added to food in the manufacturing process. This is in contrast to the small amount of salt naturally present in most foods or what is added at the table or at home in cooking.
Salt can be a desirable taste, increasing the palatability of foods in addition to helping preserve it, which is why it is commonly added to processed foods. The combination of salt and fat together is thought to promote passive over-consumption of foods.
Having a greater liking for salty and fatty foods is associated with eating more kilojoules overall, uncontrolled eating and overweight in children. This link between overconsumption of salty, fatty food is considered stronger than having a liking for sweet and fatty foods.
Sensory researchers from Deakin University recruited 48 healthy adults to take part in a tasting panel to investigate how salt may influence the over-consumption of fatty foods.
Over four lunchtime sessions (following a standardised breakfast that morning), each person ate a meal of macaroni and cheese where the fat and salt content had been manipulated. The four meal combinations were low-fat/low-salt, low-fat/high-salt, high-fat/low-salt and high-fat/high-salt.
Participants were encouraged to eat as much as they wished until feeling full. Eating rate, meal agreeability and subjective ratings of hunger and fullness were recorded.
Eleven percent more kilojoules were consumed when the meals eaten were high in salt irrespective of whether the fat content was high or low. The fat content of the meal didn’t result in people eating more food by weight but because of its greater energy density it meant more kilojoules were eaten.
People who were considered to be sensitive to the taste of fat ate less of the high-fat meal, but only if it was also low in salt. Ratings of hunger before, and fullness after, each meal were similar and unaffected by the meal composition.
This small-scale laboratory study points in the direction of the saltiness of food being able to influence passive over-consumption for foods high in fat.
In a time when there are too many discretionary food choices available that meet the criteria for being high in fat and salt, then this research helps explain why such food could be an important driver of excess eating and subsequent weight gain.