The role of dietary fat in body fat distribution is not well known.
However, some interesting results from the LIPOGAIN study were published in the July, 2014 issue of Diabetes.
This study compared the effects of overfeeding saturated and polyunsaturated fat on fat accumulation and body composition.
Here is a detailed summary of the findings.
Visceral fat accumulates in the abdominal cavity, around organs such as the intestines, liver and pancreas.
Conversely, ectopic fat accumulates inside the organs themselves, mainly the liver and pancreas.
Both visceral and ectopic fat are associated with an increased risk of chronic disease, such as heart disease and type 2 diabetes.
Combined, the adverse health consequences of visceral and ectopic fat are known as metabolic syndrome. For this reason, well-designed research on the causes of visceral and ectopic fat is extremely valuable.
A team of Swedish scientists set out to investigate the effects of eating high amounts of saturated fat and polyunsaturated fat on body composition and the accumulation of visceral and ectopic fat.
Overfeeding Polyunsaturated and Saturated Fat Causes Distinct Effects on Liver and Visceral Fat Accumulation in Humans.
BASIC STUDY DESIGN
This was a 7-week, double-blind, randomized, parallel-group trial in 39 young and normal-weight men and women.
The purpose of the study was to compare the effects of eating high amounts of either saturated fat or polyunsaturated fat.
Participants were randomly assigned to one of two groups:
- Saturated fat group: Participants were overfed with muffins high in saturated fat for 7 weeks. The fat was in the form of refined palm oil, which is rich in palmitic acid, the most common saturated fat in the modern diet.
- Polyunsaturated fat group: Participants were overfed with muffins high in omega-6 polyunsaturated fat for 7 weeks. The fat was in the form of refined sunflower oil, which is rich in linoleic acid.
The amount of muffins was adjusted so that each participant would achieve a 3% weight gain during the study period.
On average, the daily amount of oil added to the muffins was about 40 grams, and the calorie excess was 750 kcal per day.
The researchers measured total body fat, visceral fat, abdominal skin fat, liver fat, pancreatic fat and lean tissue.
Bottom Line: This study was a randomized controlled trial in healthy, normal-weight individuals. It compared the effects of overeating palm oil and sunflower oil on fat accumulation and body composition.
FINDING 1: FAT MASS AND LEAN MASS GAIN WERE AFFECTED
Participants in both groups gained equal amounts of weight, or 1.6 kg (3.5 lbs).
However, those who were fed saturated fat gained significantly more fat mass, whereas polyunsaturated fat led to a greater increase in lean mass.
In fact, the ratios of lean and fat tissue gain in the polyunsaturated and saturated fat groups were approximately 1:1 and 1:4, respectively.
The chart below shows changes in fat mass and lean mass in both groups.
This difference remained, even when total body water content was taken into account.
These findings are supported by previous studies, one in postmenopausal women and one in rats.
However, exactly how this works is unknown. It is also unclear what the current study’s increase in lean tissue actually represents or signifies.
Bottom Line: Eating high amounts of saturated fat caused more fat accumulation than eating polyunsaturated fat. Additionally, polyunsaturated fat appeared to cause a greater increase in lean mass.
FINDING 2: SATURATED FAT CAUSED MORE VISCERAL FAT GAIN
There are two types of belly fat:
- Subcutaneous: This type of belly fat is stored directly underneath the skin.
- Visceral: This type of belly fat is stored inside the abdominal cavity, surrounding the intestines, liver and pancreas.
Visceral fat is much more harmful than subcutaneous fat, and is associated with various chronic diseases.
In the present study, participants who were fed saturated fat gained significantly more visceral fat, compared with those who got polyunsaturated fat. In fact, the difference was nearly two-fold.
The chart below shows the differences in visceral fat changes between groups.
These results suggest that overeating polyunsaturated fat may cause less fat accumulation in the abdominal cavity, compared to saturated fat.
That being said, overeating is still unhealthy, no matter what you are eating — overeating polyunsaturated fat just seems to be less bad.
Bottom Line: Eating high amounts of saturated fat from palm oil caused more visceral fat accumulation than eating polyunsaturated fat from sunflower oil.
FINDING 3: SATURATED FAT CAUSED MORE LIVER FAT GAIN
Participants who were overfed with saturated fat gained significantly more liver fat than those who ate polyunsaturated fat.
The chart below shows the differences in liver fat changes between groups.
These results are well supported by several other studies.
Observational studies have found high dietary intake of saturated fats, and low intake of polyunsaturated fats, to be associated with increased liver fat.
Fatty livers also contain low levels of polyunsaturated fat. Additionally, a clinical trial found that the polyunsaturated fat in sunflower oil reduced liver fat, compared to a diet rich in saturated fat.
Accumulation of liver fat may lead to an adverse condition known as non-alcoholic fatty liver disease (NFLD). NFLD is present in up to 75% of obese people.
Fatty liver is believed to contribute to the development of many chronic diseases, such as type 2 diabetes and metabolic syndrome.
Bottom Line: Eating high amounts of saturated fat from palm oil caused greater liver fat accumulation than eating polyunsaturated fat.
FINDING 4: PANCREATIC FAT DECREASED IN BOTH GROUPS
On average, pancreatic fat decreased by 31%. There was no significant difference between groups.
This unexpected finding cannot be explained based on the study’s results, and needs to be confirmed by other studies before any solid conclusions can be reached.
Bottom Line: Pancreatic fat decreased significantly in both groups. The finding needs to be confirmed in other studies before any conclusions can be made.
This high-quality study appears to be well-designed and executed. Nevertheless, there are several limitations worth mentioning.
SUNFLOWER OIL CONTAINS MORE VITAMIN E
Sunflower oil contains more vitamin E than palm oil, and vitamin E may reduce liver fat. However, the amount of vitamin E in the sunflower oil was probably too low to have any significant effects.
THE RESULTS MAY NOT BE GENERALIZED
The study tested palm oil and sunflower oil, and may not be generalized to all saturated or polyunsaturated fatty acids.
OTHER NUTRIENTS MAY PLAY A ROLE
The dietary context may play an important role in how the body reacts to high amounts of fat.
The muffins provided to participants were also high in fructose and refined carbs, which could have affected the findings.
THE STUDY EXAMINED ONLY LEAN INDIVIDUALS
All study participants were lean, so the results may not apply to obese or diabetic individuals.
Bottom Line: The study was well designed and executed. There are a few limitations, so the results should not be generalized.
SUMMARY AND REAL-LIFE APPLICATION
This study shows that dietary fat type may affect fat distribution and body composition.
To summarize the findings:
- High amounts of palm oil (palmitic acid) led to greater liver and visceral fat gain, compared to sunflower oil.
- High amounts of sunflower oil (linoleic acid) led to almost a three times greater increase in lean body mass, compared to palm oil.
Simply put, palm oil caused fat accumulation in places associated with adverse health outcomes. Conversely, sunflowers oil caused less fat gain overall and much greater gain in lean mass.
These results are of limited value for health-conscious consumers, since they may only apply to those that are overeating and gaining weight. However, a previous study showed a similar effect during a weight-maintenance diet.
That being said, this doesn’t necessarily mean that saturated fat is unhealthy, only that eating too much of it may have worse consequences compared to eating an equal amount of polyunsaturated fat. At least in the context of a high-calorie diet.