How Does the Nervous System Control Food Intake & Prevent Obesity? (NPY)

Stress Management

Psychological stress increases NPY, and NPY in turn increases food intake; researchers believe that this is the foundation of “stress eating.” In other words, NPY makes you want to eat when you’re upset [R].

Chronic stress also increases the hunger hormone ghrelin, which in turn stimulates NPY [R].

Stress is known to cause weight gain. Stress increases cortisol and dynorphin, both of which cause weight gain [R, R, R].

It also increases glutamate, which increases appetite, while decreases NGF and BDNF, both of which are appetite suppressants [R].

Additionally, it makes the brain resistant to serotonin, a neurotransmitter that also suppresses appetite. Stress also causes resistance to dopamine, which may cause us to eat more as we’ll need to eat more food for the same rewarding effects [R, R, R].

Stress directly increases NPY, so stress management strategies are important if you want to decrease NPY.

Dietary Fiber

In one study, people with detrimental NPY variants responded better to increased intake of soluble fibre than those without the potentially bad alleles. Participants with detrimental NPY variants experienced greater decreases in all measured markers of cholesterol, sugar metabolism, and heart health when they consumed fiber in the form of psyllium husk [R].

Fiber, both from foods and supplements, is known to increase satiety after a meal and decreases subsequent hunger. Studies suggest that an additional 14 g of fiber per day is associated with a 10% lower energy intake and weight loss [R].

How much is 14g? To put it into perspective, in the US, the average fiber intake is around 15 g/day which is only half of the recommended amount [R]. 

In a meta-analysis of 62 trials with over 3,800 people, soluble fiber modestly but significantly improved body weight and decreased waist circumference even without calorie restriction [R]!

Vegetables are rich in soluble fiber, which has been shown to cause weight loss in some studies. Fiber gets broken down by bacteria in the digestive tract to produce butyrate, which has weight loss effects in animals [R, R, R, R].

Low Energy Density Foods

People with detrimental NPY variants may respond better to and lose more weight from low-calorie diets [R].

Some human research suggests that eating the exact same food, except made in a soup instead of as solid food, makes people feel more satiated and eat significantly fewer calories [R, R].

The idea is that soup has a very low energy density; that is, you would have to eat much more soup by weight than other foods to get the same number of calories. In several human studies, dieters who ate less energy dense foods lost more weight than those who ate foods with a high energy density [R, R, R].

In one study, women who ate low energy density soup lost 50% more weight than women who ate an energy-dense snack [R].

People with detrimental NPY variants may respond better than others to dietary fiber (such as from psyllium husk) and low-calorie diets.

Berberine

In rats, feeding a high-fat diet increases NPY levels; this increase was reversed in those given supplemental berberine [R].

Berberine is an alkaloid with potent metabolic effects. People use berberine as a supplement to support weight control and glucose metabolism.

Berberine supplementation reduced BMI and enhanced leptin sensitivity in 37 patients with metabolic syndrome. In another study, it caused an average weight loss of 5 lbs (2.3 kg) and lowered blood lipids [R, R].

According to a 2020 review of human and animal studies, berberine might contribute to weight loss by improving gut microbiota and glucose and fat metabolism [R].

Berberine, a popular supplement for weight loss, decreased NPY in rats fed a high-fat diet.

EGCG

In rats, EGCG normalized NPY expression which had been dysregulated by a high-fat diet [R].

EGCG caused between 0.2 and 3.5 kg of weight loss in limited human studies. Green tea, meanwhile, is hypothesized to make us burn more calories, even at rest. In most studies, this amounts to a modest 3-4% increase in energy, though some studies have shown an increase as high as 8%. For a 2,000 calorie diet, 3-4% amounts to an additional 60-80 calories per day [R, R, R, R, R, R].

In one study of 60 obese individuals, the group taking green tea extract lost 7.3lbs and burned 183 more calories per day (on average) after 3 months [R, R].

According to a review of 11 studies, green tea extract or EGCG can slightly improve weight loss and maintenance. However, a Cochrane database review of 14 studies regarded the change in weight as nonsignificant in most studies, so the evidence is inconclusive [R, R].

The majority of weight loss trials used special extracts with higher concentrations of active ingredients (catechins and caffeine), compared with regular tea. Hence, it may be necessary to take an EGCG-rich green tea extract for beneficial effects [R].

EGCG, the most important active compound in green tea and a promising supplement for weight management programs, may help normalize NPY levels.

CLA

Conjugated linoleic acids (CLA) are poly-unsaturated fatty acids. In rats, CLA injected into the brain decreased expression of NPY. CLA can cross the blood-brain barrier, so this study may help explain CLA’s possible uses in weight management [R, R].

A study done in overweight Chinese subjects found that CLA supplementation (twice daily dissolved in milk) helped with weight loss over a 12-week period [R].

The supplementation was found to reduce body weight, reduce BMI, reduce total fat mass, and reduce fat percentage [R].

The treatment also reduced waist to hip ratio and reduced subcutaneous fat mass [R].

Studies have shown that CLAs decrease lipid storage by increasing the rate of fat breakdown in fat tissue [R].

It should be noted, though, that in a similar study, CLA supplementation did not prevent weight or fat regain in obese peoples after initial weight loss [R, R].

It should also be noted that some studies have found no association between CLA and weight loss [R, R, R].

Conjugated linoleic acids (CLA) directly decrease expression of NPY in the brain. Supplementation with CLA has produced some positive results in clinical weight loss trials.

In rats, metformin directly decreases NPY expression in the hypothalamus, with the most marked reduction 4 hours after consuming the drug [R].

Metformin decreased food consumption and induced weight loss in a clinical trial on 12 obese women with type 2 diabetes. Metformin may help you lose weight if you have type 2 diabetes and your doctor prescribes you this medication. You may discuss with your doctor if it may be recommended in your case [R].