Beyond Single Nutrients-Looking at the Influence of an Entire Range of Food Groups for their Effect on Fatty Liver Deposits

Effects of Sugar Consumption Cannot be Sugar-coated

My kid loves to attend birthday parties and this is no surprise but being an introvert who doesn’t even open her mouth to ask for a glass of water to the host the fact that she runs to these get-togethers is amazing indeed. But this happiness of mine was short-lived once I realized that she loved eating the creamy cakes, greasy fries and drinking chilled soft-drinks (all of which are almost never present in my house) with no intention of even wishing the birthday kid! She is not an exception and there are many other kids with a similar state of mind living in this world amongst whom many of them are bad victims of obesity.
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Obesity exists as a public health epidemic affecting both children and adults alike. Abdominal obesity has affected innumerable number of people as reducing tummy fat has become almost next-to-impossible for individuals. Fat is not our enemy and it is a macronutrient that’s very much needed by our body for proper functioning but we do have good and bad fat whose imbalance creates havoc in each of those whose dietary intake is not well-balanced. Such abdominal obesity is a major risk factor for metabolic diseases such as type 2 diabetes (T2DM), cardiovascular diseases (CVD) and non-alcoholic fatty liver disease (NAFLD). Fat accumulation can be visceral and subcutaneous and any type of fat accumulation is dangerous. But visceral fat causes more harm as it is the fat lining internal body organs. The higher risk for CVD and other diseases due to abdominal obesity is due to the accumulation of fat in non-adipose tissue. Such visceral adipose tissue (VAT) and hepatic triglyceride content (HTGC) are linked to metabolic risk factors including insulin resistance, coronary artery disease and cardiovascular disease. VAT releases free fatty acids (FFA) and cytokine secretion which together with insulin resistance result in fat accumulation in the liver and higher risk of T2DM and CVD. So, this makes both liver and visceral fats the main fat regions that need immediate intervention to prevent cardiometabolic disease in the form of physical activity and dietary changes.

Studies show that dietary fibre, calcium and phytochemicals were inversely related to visceral fat deposits; following a healthy dietary intake and intake of medium-chain triacylglycerols show an inverse association with visceral fat and subcutaneous fat and studies show that increased energy intake during childhood years increases the risk of non-alcoholic fatty liver disease (NAFLD) irrespective of macronutrient intake. All these studies and other related ones focus on one single nutrient and its impact but it would be better to study the effects of food groups and foods together as foods might have multiple nutrients acting and interacting with each other brining in various effects. Though we know that fruits, vegetables and whole grains have a positive impact in reducing the risk of diseases and aid in weight maintenance/loss we don’t have much knowledge about the relationship between food groups and ectopic fat deposit. A group of researchers tried to understand the relationship between dietary intake of food groups and visceral and liver fat content in a population-based cohort.

Netherlands Epidemiology of Obesity (NEO) Study
The NEO is a prospective cohort study of 6671 individuals aged between 45 and 65 years with a self-reported BMI≥27 eligible for participation. All of them filled a questionnaire about demographic and clinical information and the next day visited the NEO study centre after an overnight fast. The study assessing relationship between food groups and fat content is a cross-sectional analysis of the baseline measurement of participants (who were chosen after imposing all exclusion criteria) with a measurement of VAT.

Ethnicity was self-reported, tobacco smoking was categorized as current, former or never smoking; education level was self-reported; BMI calculation were made; menopause state was mentioned; basal metabolic rate was calculated based on age, sex, height and weight and participant’s frequency and duration of physical activity during leisure time was measured.

A self-administered food frequency questionnaire (FFQ) helped the participants answer questions on the frequency (times per day, times per week, times per month or never) of food intakes during the past month. Serving size was estimated for calculating calories in terms of pieces of fruits, spoons of potatoes, etc. Nutrient intake and total energy were calculated using the Dutch Food Composition Table. Depending on nutrients, sources and biological effects foods were categorized into different food groups with the help of the FFQ. This included classifying them under dairy (milk, cheese, yogurt and butter), fruits and veggies, meat, sweet snacks (candy and cake), fish and plant-based fats and oils (margarine and oils). Calorie value of each food group was divided by the total calorie intake per day to find the total energy percentage. VAT and HTGC were measured in appropriate ways.  Of the 6671 who were interested in the study only 2304 were included in the analysis due to various exclusion criteria including diabetes, elevated energy intake, incomplete FFQ, energy-restricted diet intake and unavailable data on smoking.

The research team assessed the reproducibility of the dietary intakes of the food groups in 100 participants who completed the FFQ twice with only a 3-month gap between them. It was seen that after adjusting different factors dietary intake of fruits and vegetables was linked to 1.12 cm2 less VAT; intake of plant-based fats and oils was linked to 13.9 cm2 less VAT and dietary intake of fish, dairy, meat and sweet snacks was not linked with VAT. Introspecting on the food groups minutely showed that yogurt created a negative association between dairy and VAT in women whereas dietary intake of dairy, meat and fruits and vegetables was more strongly linked to VAT in postmenopausal women than in premenopausal women.

Of 1715 participants with HTGC measurements dietary intake of sweet snacks was associated with a 1.19-fold higher HTGC while intake of fruits, dairy, vegetables, fish, meat and fats and oils were not linked to HTGC.  Finetuning showed that vegetables were strongly associated with HTGC than fruits, and yogurt was linked with liver fat of all the dairy components. Sweet snacks and HTGC was linked strongly in premenopausal women than in postmenopausal women. The study shows that fish and meat are not associated with visceral fat, dairy was negatively associated with visceral fat and sweet snacks intake is linked to more visceral fat.

Effect of Macronutrients on Liver Fat Content
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Hypercaloric Diet
Most of the studies involve a hypercaloric diet where most of the participants are males with a BMI<27 who were overfed a fructose diet. Such consumption leads to increased fatty deposits in the liver. Men almost consumed >180 g/d of fructose compared to the recommended 30-50 g/d. fructose consumption is generally higher in the adolescent population. When studies tried to overfeed calories while reducing the quantity of fructose consumed there was no increase in fatty liver content even after 28 days. Fructose and glucose have similar effect on liver fat accumulation. We don’t consume fructose as an individual product but it is a by-product of fruits and of those containing free sugars (sugar-sweetened beverages or confectionaries). A study by Maersk et al compared the effects of ingesting 1L/d of a sugar-sweetened beverage, calorie-matched milk, non-nutritive beverage or water for 6 months. It was seen that consuming a sugar-sweetened beverage increased liver fat by 132-149% compared to other beverage groups but it must be noticed that as the different groups were having gender disparity and diets too were not standardized between the groups. Sevastianova et al. researched on a 3-week hypercaloric diet where 98% of excess calories was given in the form of added sugars such as candy, fruit juice and sugar-sweetened beverages. There was almost 27% increase in liver fat at the end of the high-sugar diet. A couple of studies showed that alongside increased total fat intake the fatty acid composition of a high-energy diet might also be an important regulator of lover fat accumulation.

Bortolotti et al. showed that while increased fat intake elevated liver fat by 90% supplementing it with protein led to a reduction in liver fat accumulation compared to a high-fat diet. A protein-rich diet helped in moderating liver fat accumulation to a great extent. Excess consumption of fat and sugar led to increased fatty deposits in the liver.

Hypocaloric Diet
Various studies show that significant reduction in total calorie intake was linked to a significant reduction in liver fat content. This shows that weight loss interventions are standard or helpful strategies against NAFLD. A study by Browning et al. showed that reducing carbohydrate intake helped in reducing liver fat content than reducing total calories without changes to the macronutrient composition of the diet but some studies show that carbohydrate intake has little influence on change in liver fat content. But a large number of studies showed that total calorie deficits is the need of the hour for decreasing liver fat and alterations in macronutrient composition have little influence.

Isocaloric Diet
The difference in nutrient intake modulates liver fat content. Altering macronutrient composition to a higher fat intake leads to increase in liver fat content. This is applicable only to increase in SFA levels and increasing MUFA and PUFA levels reduce liver fat content.
Consumption of a hypercaloric diet increases liver fat content, consumption of a hypocaloric diet decreases liver fat content and consumption of dietary sugars requires further clarity as the effect depends on the form in which they are consumed.

Bottomline
It has been proposed that obese/overweight children with fatty liver disease reduce fatty deposits in the liver by refraining from drinking soft drinks and fruit juices and cutting down consumption of sugary foods. Physicians advise patients with a fatty liver disease to cut down on excess sugar intake that’s generally high in processed foods and exercise regularly. Its tempting when you look at the glossy supermarket aisles stuffed with your favourite candies and treats. It is always advisable to stay away from the middle aisles that contain these stuffs. Avoid storing junk foods at home as these once again disturb the individual provoking him/her to eat them when its right before the eye. Staying on a healthy diet, avoiding excess consumption of processed foods and exercising regularly keeps you away from weight gain and fatty deposits anywhere in the body, especially the liver.

References
Sweet Snacks are Positively & Fruits & Vegetables are Negatively Associated with Visceral or Lover Fat Content in Middle-Aged Men & Women: https://academic.oup.com/jn/article/149/2/304/5290057

Influence of Dietary Macronutrients on Liver Fat Accumulation & Metabolism: https://jim.bmj.com/content/65/8/1102

To Avoid Fatty Liver, Avoid Sugary Foods & Drinks: https://www.nytimes.com/2019/01/22/well/eat/to-fight-fatty-liver-avoid-sugary-foods-and-drinks.html