Recently, the results of a new study were published. This research scrutinized the benefits of eating less fat in reducing the levels of fat stored in the body and especially in places never intended for fat storage. The human body contains tissues specialized for the storage of fat. These tissues, known as adipose tissues, are composed of fat cells (adipocytes) and are energy storing cells that contain large globules of fats (lipid droplets) surrounded by a network of structural fibers. Adipose tissue is located beneath the skin (subcutaneous fat), around internal organs (visceral fat) and in the central cavity of bones (bone marrow fat). In addition, small amounts of fat cushion and protect various body parts (1).
In obesity, storage of fat can extend to tissues that normally handle only small amounts of lipids. This is called ectopic fat storage, and it can occur in the liver, kidney, heart, pancreas and muscles. Ectopic fat can interfere with the function of the affected cells and organs. Specifically, fat stored in the liver and muscles impairs the ability of insulin to signal the cells to absorb glucose, creating insulin resistance and is linked to high blood sugar levels and the development of type-2 diabetes. Accumulation of fat in the heart is associated with heart failure. Fat build-up in the kidneys contributes to alterations in kidney function, directly increasing the risks of developing high blood pressure, diabetes and chronic kidney disease (2,3).
The study (4);
This research, published in late 2020, is a randomized clinical trial that was conducted on 244 participants aged 25 to 75 years with a body mass index (BMI) of 28 to 40. Subjects who smoked, drank alcohol or used drugs, had diabetes, were pregnant or lactating or currently eating a vegan diet were excluded.
Participants were randomly assigned (in a 1:1 ratio) to either an intervention group or a control group. The intervention group was asked to follow a low-fat vegan diet containing approximately 75% of energy from carbohydrates, 15% from protein and 10% from fat and consisting of vegetables, legumes, grains and fruits for 16 weeks. Animal products and added fats were excluded. The intervention group participants received vitamin B12 supplements with a daily dose of 500 mcg. They also attended weekly classes for detailed diet instruction and cooking demonstrations. The control group was asked to make no changes in their diet. Both groups were advised to limit their alcoholic beverages to 1 serving *** per day for women and 2 servings per day for men. Both groups were to maintain their usual amounts of exercise and their current medications (unless altered by their personal physician).
***A standard drink serving in Canada has 17.2 mL of “pure alcohol,” which represents one 12-ounce beer (5% Alcohol By Volume), a 1.5 ounce shot of liquor (40 per cent Alcohol By Volume) or a 5-ounce pour of 12% Alcohol By Volume wine.
Data was collected at the beginning of the trial and at 16 weeks. After an overnight fast, laboratory measurements were taken. These included height and weight as well as body composition including total body fat and visceral fat volume. Insulin secretion was measured after a standardized breakfast of Nestle’s meal replacement, Boost Plus (50% of calories from carbohydrate, 34% from fat and 16% from protein), after which the glucose level in the blood was followed over the next 180 minutes. Lipid levels, including total cholesterol, HDL-cholesterol, LDL-cholesterol and triglycerides were also obtained. Insulin resistance and insulin sensitivity were evaluated and resting energy expenditure and after-meal metabolism measured. Physical activity levels were assessed. Last, but certainly not least, the level of fat in the liver and muscles was determined in a sub-group of 44 participants.
Here are the results (4);
Energy intake (calories) decreased in both groups but more so in the intervention group.
In the intervention group, intake of carbohydrate and fiber increased while fat, protein and cholesterol intake decreased. These factors did not change significantly in the control group.
Physical activity decreased by a small amount in both groups.
Body weight decreased by an average of 14 pounds in the intervention group and by 1 pound in the control group. This weight loss was due to a reduction in body fat. The intervention group participants showed significant decreases in both fat mass and visceral fat volume.
Total cholesterol decreased by 0.5 mmol/L in the intervention group. LDL-cholesterol decreased by 0.4 mmol/L in the intervention group. There were no significant changes in total cholesterol or LDL-cholesterol in the control group.
In the intervention group, fasting blood insulin concentration decreased, insulin resistance decreased and insulin sensitivity increased. No changes were observed in the control group.
After meal energy expenditure (after-meal burn of calories) increased by 18.7% in the intervention group. No significant change occurred in the control group.
In the subset of 44 participants, the liver fat level at the start of the trial was generally in the normal range. Nonetheless, lipids in the liver decreased by 34.4%. In the muscles, lipids decreased by 10.4% in the intervention group. Both levels remained unchanged in the control group. The lipid decreases in the liver were associated with a change in body weight but not with changes in reported energy intake or fiber consumption.
As fat levels in the liver decreased, insulin sensitivity increased.
As total body fat decreased, both the lipid levels in the muscles and insulin resistance decreased.
Conclusions of this trial (4);
Consumption of a low-fat vegan diet reduced body weight through a reduction in energy intake and an increase in “after-meal burn”. These effects occurred despite there being no restrictions on the amount of food eaten. In addition, weight loss was sufficient to reduce the fat levels in both the liver and in the muscles, thereby improving blood sugar control, reducing blood insulin concentration and reversing insulin resistance in the liver. Researchers propose that this improvement in insulin sensitivity is the result of the lowering of lipids within the cells. Fats inside cells reduce the ability of insulin signals to allow cells to accept the intake of glucose and thus create insulin resistance.
This research is of the highest quality. It uses randomization to place participants into the intervention or the control group and includes a true control group. Consequently, its results can be directly attributed to the interventions its participants received during the trial. Randomization is also beneficial in terms of a more accurate statistical analysis and the significance of its results. Although no study on its own can prove causality, randomization reduces bias and can expose cause-effect relationships between an intervention and outcome (5,6).
The result of this study clearly illustrate the beneficial effects of removing fat from storage in places it is not meant to be stored;
- Fat stored in the liver and muscles impairs the ability of insulin to signal the cells to absorb glucose thus causing insulin resistance and leading to high blood sugar levels and the development of type-2 diabetes.
- A low-fat vegan diet containing approximately 75% of energy from carbohydrates, 15% from protein and 10% from fat and consisting of vegetables legumes, grains and fruits removes fat from the liver and muscles thereby lowering insulin resistance, increasing insulin sensitivity and reducing the risk of developing type-2 diabetes.
- The same diet can promote healthy weight loss through the removal of fat from tissues not designed to store fat and through increasing the number of calories burned after eating. These beneficial effects occurred despite there being no restriction placed on the amount of food eaten. Lead researcher, Dr. Hana Kahleova, points out that burning more calories after every meal can be of significant help in weight management.
- The same diet can also significantly lower total and LDL-cholesterol blood levels.
- Reducing fat in places not designed to store fat can reduce the risk of developing other chronic conditions such as heart failure and kidney disease
Adding to all these benefits is the higher level of satisfaction resulting from eating a plant-based diet compared to consuming a meat-based diet. Research from 2020 shows that when people eat a meal containing meat, they experience decreased secretion of a hormone that affects the reward circuits in the brain. A plant-based meal produced better blood flow in brain areas associated with food intake and higher meal satisfaction (7).
Increased insulin sensitivity
Decreased insulin resistance
Lower blood sugar levels
Reduced risks of developing type-2 diabetes, high blood pressure, heart failure and chronic kidney disease.
Significant weight loss through loss of body fat
Reduction of fat stored where it should not be
Higher “after-meal burn” of calories
Lower cholesterol levels
Greater satisfaction with the food you’re eating
What more could a person ask for?
2 van Herpen, N.A., Schrauwen-Hinderling, V.B. Lipid accumulation in non-adipose tissue and lipotoxicity. Physiol Behav. 2008 May 23; 94(2): 231-241. doi: 10.1016/j.physbeh.2007.11.049.
3 Guebre-Egziabher, F., Alix, P.M., Koppe, L., Pelletier, C.C., Kalbacher, E., Fouque, D., Soulage, C.O. Ectopic lipid accumulation: A potential cause for metabolic disturbances and a contributor to the alteration of kidney function. Biochimie. 2013 Nov; 95(11):1971-1979. Doi:10.1016/j.biochi.2013.07.017.
4 Kahleova, H., Petersen, K.F., Shulman, G.I., Alwarith, J., Rembert, E., Tura, A., Hill, M., Holubkov, R., Barnard, N.D. Effect of a Low-Fat Vegan Diet on Body Weight, Insulin Sensitivity, Postprandial Metabolism, and Intramyocellular and Hepatocellular Lipid Levels in Overweight Adults: A Randomized Clinical Trial. JAMA Netw Open. 2020 Nov; 3(11): e2025454. Doi: 10.1001/jamanetworkopen.2020.25454.
5 Stang, A. Randomized Controlled Trials – an Indispensible Part of Clinical Research. Dtsch Arztebl Int. 2011 Sep; 108(39): 661–662. Doi: 10.3238/arztebl.2011.0661.
6 Hariton, E., Locascio, J.J. Randomised controlled trials—the gold standard for effectiveness research. BJOG. 2018 Dec; 125(13): 1716. Doi: 10.1111/1471-0528.15199.
7 Kahleova, H., Tintera, J., Thieme, L., et al. A plant-based meal affects thalamus perfusion differently than an energy- and macronutrient-matched conventional meal in men with type 2 diabetes, overweight/obese, and healthy men: A three-group randomized crossover study. JAMA Netw Open . 2020 Nov 2; 3(11): e2025454. Doi: 10.1001/jamanetworkopen.2020.25454.