It’s the time of the year when we are in a festive mood as Christmas and New Year are very near. We are looking into various party options, the best DJ’s who can make our New Year Eve awesome and the best cuisines that could be a treat to our taste buds. Besides these, plans for Christmas meet ups and cake exchange roundups are happening in full swing. Among all this buzz, are you one of the very few who stands grounded resisting all these temptations but enjoys the buffet spread and the food varieties sticking to optimal portion sizes? If yes, it should be highly appreciated as most of us are not wired that way. The sight of a yummy doughnut or a lip-smacking burger dissolves all our resistance to eat healthy food and our mind never becomes satisfied until we eat it. Moreover, New Year is the time of the year where we make commitments to ourselves to become better taking up goals and resolutions that once again disappear into thin air in course of a month or two. Obesity and overweight, two of the most debilitating conditions affecting our health has become a global concern owing to their extreme side effects on the quality of life of individuals. They pave way for serious health problems including cardiovascular diseases, cancers and other conditions as well. Calories consumed is more than calories burned resulting in an energy imbalance that is the root cause for excess fat accumulation in the body.
The primary deal now is to identify the underlying mechanisms that trigger such excessive energy intake in order to control the obesity epidemic. We do have a number of research studies probing into the genetic, hormonal and metabolic reasons associated to dietary intake and weight gain. Mankind has strong ties with his previous generations carrying on their genetic traits but the surrounding environment also has equal influence on his/her actions. We safely blame our genes for any negative consequences of our action, for our slow metabolism or even our laziness leaving behind all the efforts that could have helped us overcome these negative effects in life. So, indeed the fact that number of studies helping us understand the underlying and modifiable neural mechanisms that motivate the decisions about ‘what’ and ‘how much’ are fewer in number comes as no surprise to us.
Drug and alcohols were some of the common addictions decades back but mankind slowly started digging his own grave by becoming addicted to smartphones, tablets and games. Gaming addiction has been declared as an official addiction by the World Health Organization. Food has been the first love for many who are ready to give up several things for it. These guys can never resist the temptation of highly palatable, calorie-rich foods that’s now been designated as an addictive behavior that’s similar to other addictions. An analysis on those who eat excessive portions reveal that they blindly select their favorite foods thinking about the short-term happiness totally turning a blind eye to the long-term consequences staying put in a situation where they have lost the ability to make optimal food-related choices. Researchers feel that three key neural systems that include the following might provide explanation for the inability to control temptation of food and the development of less-healthful eating habits:
Study on the Neural Systems Triggering the Temptation to Eat Tasty Food
The study included 30 young healthy adolescents (17 of them were females) aged around 19.7 years whose average BMI was 23.1. None of them were under treatment for obesity and the research team ensured to exclude those who were suffering from neuropsychiatric disorders, medications or issues such as anxiety, bipolar disorder, psychoses or substance abuse that could affect neuroimaging results with the help of a technique called SCID. All the participants were asked to answer a 41-item questionnaire that probed into the participant’s history of diabetes, hypertension, lungs, heart, kidney or liver disease. Questions on head trauma, neurological diseases, use of any medications, smoking, alcohol use and caffeine consumption were present in the same questionnaire. Participants with positive answers to a history of head injury, treatment for obesity or neurological disease were excluded from the study.
All the participants were requested to come for completion of their behavioural task and scan. They were asked to refrain from any intense physical activity 24 hours prior to the scan but there was no restriction in meal and food habits. Height and weight measurements were taken before the scan, 1 24-hour dietary recall was done and the participants rated their hunger level from a scale of 1 (not hungry) to 10 (extremely hungry) to ensure that none of them were in a deprived state. Those who had a score >5 were asked to return back some other time after eating a normal meal. All the participants performed two food-specific go/nogo taks: one low-calorie food go and high-calorie food nogo task (LGo task) and the second, a high-calorie food go and low-calorie food nogo task (HGo task). Cucumbers, celery, broccoli and carrots were some of the foods included in the low-calorie food images while high-calorie food images included cookies, ice creams, potato chips and cookies. Each of them were asked to press a button when they were ready to go to trial and withhold responses to the nogo trials. There were 120 go trials (75%) and 40 nogo trials (25%) occurring in a random order such that Nogo trials also has equal probability as the Go trials also ensuring that no two Nogo trials appeared consecutively. Every image was present for 500ms and every task had a maximum duration of 8 minutes.
The participants exhibited normal intelligence (IQ) and working memory/functioning. Each of the individuals reported consuming 2.4±1.6 servings/day/1000 kcal of low-calorie foods (fruits and vegetables) and 1.8±1.3 servings/day/1000 kcal of high-calorie foods (such as sugar-sweetened and fatty foods). It was good to realize that all of them consumed more servings of low-calorie foods comparatively irrespective of age and hunger rating. But there was a gender difference reported with females consuming more low-calorie foods than high-calorie foods in comparison to males. Participants made frequent errors and faced hard times inhibiting responses to high-calorie food cues in the LGo task and reaction time was also longer in this task. Participants were willing to press the button more willingly when they were presented with high-calorie food images in the HGo task.
Reaction time for the trials in the HGo task was negatively correlated with BMI and high-calorie food consumption indicating that people with higher BMI values responded more readily to high-calorie foods. It was also observed that inhibiting response to high-calorie foods was difficult for individuals with higher BMI and those who consumed more of high-calorie foods. The neural system showed more activation during nogo trials than go trials.
The task imposed effect on regions of the brain including bilateral frontal pole, bilateral dorsolateral prefrontal cortex (DLPFC) and ACC which were more active during the nogo trials than during go trials. The left occipital pole showed main effect of the stimuli activacted every time when a high-calorie food picture was shown in comparison to viewing a low-calorie picture. There was no interaction seen between task and stimuli in any region of the brain. Activation in the anterior cingulate cortex (ACC) comparing nogo trials to go trials was negatively correlated with BMI and high-calorie food consumption. Also, females displayed more activation in ACC than males when comparing nogo trials to go trials. Go trial results showed that high-calorie food cues were linked to higher activity in the right striatum relative to low-calorie food cues. Such increased activity in the right striatum was linked to both BMI and level of high-calorie food consumption. Males and females did not show any difference in the activation of the right striatum.
The study did show the neural basis that exists as a reason behind one’s loss of ability for self-control when shown tempting food choices and this could be used to bring about intervention strategies to reduce the consumption of high-calorie foods. This in turn reduces the rates of obesity/overweight that’s disrupting the health of people in the society.
Pre-exposure of Tempting Food Decreases Temptations
Pre-exposure of tempting food in situations that discouraged temptations improved resistance to food temptation thereon. This has been tested in normal-weight people and has shown beneficial results but we don’t have studies until now testing it on obese individuals. It is seen generally that obese people respond differently to tempting food compared to healthy-weight people-they are poor at resisting temptations and value such tempting rewards more. We have a study that took up pre-exposure of tempting food to obese people and its effect on preventing them from succumbing to temptations in due course.
The study happened in two different university labs, Greece and Belgium, which included 115 individuals of whom 77 were healthy-wight and 38 were obese participants. All the participants were inquired about their hunger levels (on a 7-point scale) and were informed of their participation in a word fluency test. Each of them was randomly assigned to a candy scrabble game (pre-exposure condition, PE) or a foam scrabble game (control condition, CTR). Each group received 30 letters which was used to form words during the game. Then, each of them received two bowls of the same volume of a tempting snack and the samples were named as A and B though in reality both the bowls contained the same snack. Each of them either received two bowls of peanut M&M’s or two bowls of Maltesers. Each of the participants were asked questions such as ‘How crunchy are these chocolate candies/crunchy nuts?’ ,’to what extent do they melt in the mouth’, etc.
Difference in the sample with respect to age and gender was observed with no difference in the average BMI. No difference in hunger levels was observed between the healthy and obese participants and within the obese group no difference in hunger levels was observed for CRT and PE condition. In the PE condition hunger levels were higher than in the CRT condition for obese participants while the healthy-wight participants ate less.
In health-weight participants, those who performed the scrabble test with candy letters (PE) ate significantly less during the subsequent taste test than the group that performed the task with foam letters. Obese-weight participants in both the groups consumed a similar number of tempting snacks. In the control group, the obese-weight participants ate less than the healthy-weight participants but the same did not happen in the experimental group.
The study showed that pre-exposure helped healthy-weight participants to consume less but the same was not observed in obese individuals.
Poor Ability to Resist Tempting Calorie Rich Food is Linked to Altered Balance between Neural Systems Involved in Urge & Self Control: https://nutritionj.biomedcentral.com/articles/10.1186/1475-2891-13-92
Pre-exposure to Tempting Food Reduces Subsequent Snack Consumption in Healthy-weight but not in Obese-weight Individuals: https://www.frontiersin.org/articles/10.3389/fpsyg.2018.00685/full
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