Can you lose weight by smelling meat? Nature sub-issue: "Odor Therapy" can promote lipid metabolism and easy weight loss, or a gospel for people who have difficulty losing weight!

You who have been struggling to lose weight,

What weight loss methods have you tried?

Dieting, weight loss products, exercise.
.
.

With the emergence of many weight loss methods, a new type of odor weight loss method began to enter the public eye, and scientists even developed some compound odor products
.
The mixed smell of mint + a little pepper will give the brain the illusion of "full" and suppress appetite; The smell of some essential oils not only soothes stress and uplifts the spirit, but can even cure puffy obesity
by boosting metabolism.
So how exactly does odor affect fat metabolism?

In fact, the association between smell and fat metabolism is not a very new thing, but scientists have not been clear about the mechanism
behind this phenomenon.
On November 14, 2022, Professor Toshiyasu Sasaoka's team from the Department of Clinical Pharmacology at the University of Toyama in Japan published the latest study in Nature Metabolism, giving the answer to the
link between odor and fat loss.
Simply put, smelling food during fasting can promote lipid metabolism in the body; When intermittent fasting is combined with food odor stimuli, blood sugar levels can be controlled and insulin resistance
prevented.

Image source: Nature Metabolism

1 During fasting, sensing food odor promotes the mobilization
of non-esterified fatty acids.

In the early stage of the experiment, mice relied on their sense of smell to explore high-fat foods, and by removing olfactory bulb comparison, it was found that mice that lost their sense of smell stopped exploring based on odor preference, and food visual stimulation had no effect
on mouse behavior.

Figure 1.
Fasted mice explored food
based on smell rather than visual information.
(Image: Nature Metabolism)

The main source of energy during fasting is adipose tissue breakdown to increase serum free fatty acids, and under 24-hour fasting conditions, normal feed (NCD) odor stimulation further increases the level of unesterified fatty acids (NEFAs) in the serum, especially increasing the levels of oleic acid and linoleic acid, reducing the ratio
of palmitic acid/oleic acid and stearic acid/oleic acid.
The above results are favorable because unsaturated fatty acids are beneficial to metabolic health
.

Figure 2.
Changes in NEFA levels in fasted C57BL/6J mice at 1 h of exposure to food olfactory or visual information
.
(Image: Nature Metabolism)

2 Mechanisms by which food odor mobilizes lipids

Studies have found that the hypothalamic melanin corticotin-4 receptor (MC4R) and sympathetic nervous system are involved in this process
.
By analyzing protein and gene expression profiles, it was found that after 10 minutes of odor stimulation during fasting, lipolysis in adipose tissue was enhanced and phosphorylation
of S6 ribosomal protein, a molecule downstream of mTOR in the liver.
One hour after exposure to odor, gene expression in soleus muscle, epididymal white adipose tissue (eWAT), and pancreas was also affected
by olfactory stimulation.

3 Pre-exposure to food odors improves post-meal fat utilization

After the use of food odor stimulation before meals, it was found to promote the utilization of postprandial fat, which is through a leptin receptor-related manner, independent of the orexinergic and dopaminergic reward pathways in the brain, increases serum triglycerides and cholesterol in chylomicrons and very low-density lipoprotein components, and promotes tissue-specific regulation of metabolic activity during re-eating, significantly increasing metabolic flow
in the liver 。 In addition, the study of the mechanism of sympathetic regulation during refeeding found that pre-stimulation of NCD odor reduced HSL phosphorylation in eWAT after refeeding and Ucp1 and Pgc1a expression
in brown adipose tissue.

4 Beneficial effects of food odor stimulation in obese states

Intermittent fasting (24 h twice a week) was found by intermittent fasting (24 h twice a week) on mice on a high-fat diet (HFD), that HFD odor stimulation had no additional effect on body weight and food intake, but reduced blood glucose levels
.
Moreover, HFD odor stimulation leads to a decrease
in levels of the insulin resistance index HOMA-ir and the insulin secretion index HOMA-β.
In the oral glucose tolerance test, peak glucose levels in the HFD odor-stimulated group decreased
.
Thus, chronic food odor stimulation increases the benefits of intermittent fasting on glucose metabolism without additional weight alteration
for diet-induced obesity.

Figure 3.
Effects of
food odor stimulation on diet-induced metabolic function in obese mice.
(Image: Nature Metabolism)

Epidemiological evidence suggests that obese, insulin-resistant or type 2 diabetic people have olfactory dysfunction, although there are also opposing views that obese people are more sensitive to
the smell of delicious and high-energy foods.
Although these studies are contradictory, olfactory sensitivity is a key factor in maintaining metabolic health, and it has been previously reported that the dynamic regulation between olfactory neurons and fat storage, different odors trigger different olfactory neurons, which in turn affect the metabolic process
of fat.

In general, smelling food during fasting can double regulate lipid metabolism, enhance lipid mobilization in the body during fasting, promote lipid utilization and control blood sugar levels
during the feeding period.
This regulation helps maintain metabolic health
in different environments in the body.

So friends who are struggling to lose weight, think about it this way, the goal of fat loss through food smell stimulation is just around the corner, but before this idea becomes a reality, controlling diet + exercise is a healthy way to lose weight!

References:

1.
 Tsuneki H, Sugiyama M, Ito T, Sato K, Matsuda H, Onishi K, Yubune K, Matsuoka Y, Nagai S, Yamagishi T, Maeda T, Honda K, Okekawa A, Watanabe S, Yaku K, Okuzaki D, Otsubo R, Nomoto M, Inokuchi K, Nakagawa T, Wada T, Yasui T, Sasaoka T.
Food odor perception promotes systemic lipid utilization.
Nat Metab.
2022 Nov 14.
doi: 10.
1038/s42255-022-00673-y.
Epub ahead of print.

2.
Mutlu AS, Gao SM, Zhang H, Wang MC.
Olfactory specificity regulates lipid metabolism through neuroendocrine signaling in Caenorhabditis elegans.
Nat Commun.
2020 Mar 19; 11(1):1450.