Animal study: low-carb diet with lots of saturated fats cuts life expectancy

Not all nutritionists are happy with the idea, but it does look as though a low-carb diet can be healthy. Take a look in our archives. But that low-carb diet must not contain too much saturated fatty acids, write researchers at the Universidade Federal do Rio Grande do Sul in Longevity & Healthspan. The Brazilians did experiments on mice.


Saturated fatty acids

After a number of epidemiological studies, now generally recognised as classics, showed that a high intake of saturated fatty acids was associated with a high risk of cardiovascular disease and other chronic diseases, traditional nutritional scientists sent saturated fatty acids to the back of the class. A number of critical and more refined scientific studies since then claim this was not necessary and that the correlations were not as strong as suggested.

When weighed up against other factors such as the amount of body fat, lack of physical exercise, smoking and drinking, the negative health effects of saturated fats in the diet are not so great. The critics suggest that the classic studies may have reported quasi correlations, and that people who eat high amounts of saturated fat also consume large amounts of sugar. Or they were fatter.


On top of that, the body can’t do an awful lot with saturated fatty acids except for burn them. Polyunsaturated fatty acids, which regular scientists say are healthier than saturated fatty acids, can also function as a raw material for all sorts of compounds and hormone-like factors that are definitely unhealthy. Say the critics.


The Brazilians tried to find out more about the effects of a low-carb diet, in which the carbohydrates had been replaced by a relatively large amount of saturated fatty acids. They fed C57BL/6 mice a diet for two years in which 60 percent of the energy was derived from fats. The main source of fat was lard. A control group was given a standard diet, in which 60 percent of the energy was derived from starch.

Half of the mice that ate a low-carb diet put on weight [DIO], the other half did not [DR].



The researchers discovered that the saturated fat diet caused both the thin and the fat mice to die sooner than the standard diet did.

After the mice had been on the high-fat diet for nearly eighteen months the Brazilians tested their memory function. They put the mice in a cage in which there were places that would give them an electric shock. Then the researchers waited a while, and put the animals back in the cage on the danger spot, and measured how long it was before the animals moved away of their own accord. The faster that happened, the better their memory.

The figure below shows that the high-fat diet reduced the mice’s memory function.



“We were not able to explain the exact mechanism by which a high fat diet increased mortality”, the Brazilians write. “However, the high energy source from saturated fat over 27 months could be implicated in increased reactive oxygen species production and oxidative stress, which is the main process responsible for aging and also a contributory factor for neurodegeneration.”

“Also, activation of inflammatory and immunological response induced by a high fat diet and/or aging may exert a negative impact and be implicated in the differences in life expectancy observed in our study.”

“In conclusion, C57BL/6 mice fed a high fat diet may develop an obese phenotype or not compared to mice fed a control diet. A high fat diet decreased the survival rate independent of body weight gain.”

High saturated fat and low carbohydrate diet decreases lifespan independent of body weight in mice.



Obesity is a health problem that is reaching epidemic proportions worldwide. We investigated the effects of a life-long high saturated fat and low carbohydrate (HF) diet on the body mass, glucose tolerance, cognitive performance and lifespan of mice.


C57BL/6J mice were fed with a HF diet (60% kcal/fat) or control diets (15% kcal/fat) for 27 months. One-half of the mice on the HF diet developed obesity (diet-induced obese (DIO) mice), whereas the remaining mice were diet resistant (DR). At 8 months of age, both DIO and DR groups had increased hyperglycemic response during a glucose tolerance test, which was normalized in 16-month-old mice. At this latter time point, all groups presented similar performance in cognitive tests (Morris water maze and inhibitory avoidance). The survival curves of the HF and control diet groups started to diverge at 15 months of age and, after 27 months, the survival rate of mice in the DIO and DR groups was 40%, whereas in the control diet group it was 75%.


AHF diet decreased the survival of mice independent of bodyweight.

PMID: 24472284 [PubMed] PMCID: PMC3922950