Microbiota and obesity

Our gut bacteria can be partially blamed for being overweight or obese. There is a causal link between the microbiota and obesity, driven in combination with overnutrition and drastic lifestyle changes.

The prevalence of obesity is reported to increase worldwide and it is a major challenge in our modern days. There are various attempts to explain the large increase in obesity, mostly due to the last three decades of research. They include calorie intake, changes in dietary composition, decrease in physical activity and changes in the gut microbiome. Is the gut microbiota contributing to the excessive weight accumulation in our body? A piece of evidence was published in 2005, when scientist found that obese mice microbiota composition is different from the healthy lean ones. An increase of Phylum Firmicutes bacteria was noticed in the obese mices, and their microbial diversity was lower than normal. This made them wonder if is obesity causing the changes in the microbiota or is the gut bacteria causing obesity? They got sample from human twins (one fat, one lean) and give them to germ free mice. The ones with bacteria from the slim ones stayed slim, the others quickly gained weight. So the conclusion was that there is a direct causal link between the gut microbiota and the weight gain. The next trials started with gut microbes from lean humans, given to obese individuals, and they improved their metabolic response and experienced weight loss. The effect lasted for few weeks when the study was done, but we do not know if the effect is sustained. Also, fecal transplant is prone to high risk of infection. We will talk later about this.

The gut microbiota is a major contributor to obesity. Our diet is another one, as the Western style diet is an example , characterized by highly processed and refined foods, rich in proteins and fats. It has a high salt, fat and sugar content, with protein mainly from red meat. This diet is the major contributor to the actual crysis of obesity and to a wide range of obesity related diseases. This type of diet leads to a low presence of bacteroidetes and akkermansia, followed by an increase in the firmicutes and proteobacteria groups. These alterations were associated with obesity and the subsecvent related chronic diseases. The high fat content causes an overload in energy leading to obesity, but the change in microbiota can also cause inflammation, which in turn can lead to many obesity related diseases.

Diet can increase obesity and obesity related diseases directly and indirectly. The evidence supporting the link between obesity and lifestyle changes is very strong. Modulation of the microbiota might help to ameliorate metabolic responses and initial weight loss attempts. Adapting the microbiota might be useful to keep a healthy weight or even to lose weight.

Next post: Undernutrition and weight loss.

See you soon.
G.

Possible solutions for obesity

There are some tested methods against obesity, and the most effective ones are:

1. Physical exercise
2. Dieting
3. Obesogenic environment
4. Surgery

Weight loss is the result of a negative energy balance (energy intake is lower than the energy expediture). For a successful weight loss, you need to decrease energy intake through diet, or to increase energy expediture through exercise. Other less used alternatives are using a fat digestion inhibitor like Orlistat or adjustment to lose more energy via feces.

This is an easy solution only in theory, but hard to put in practice. Creating long lasting habits is a must in this case, and lacking this skill leads to failure (failing to prepare is preparing to fail), In order to lose weight through diet you need to adopt a hipocaloric one, and the result is fat lose over time. Seems a bit contradictory, but you can lose weight even eating burgers and stake, as long as the energy balance is negative. Warning: any claim of fat loss diet without reducing the energy intake is a scam. The biggest the cut, the faster the loss, but we need to not forget that eventually we gonna hit a plateau as having less fat means having less weight, so the basal metabolic rate will also decrease. The magnitude of the fat loss is determined by the overall energy deficit created as a result of being on diet. Monotonous diets tend to be highly effective in causing short term fat loss due to the declining satisfaction resulting from the consumption of only one specific type of food, even if it is one that we like (we are talking here about hedonic adaptation - one chocolate is nice, twenty chocolates at once are awful). But, because monotonous diets are boring, is hard to stick to them and not return to old food habits.

In conclusion, the higher overall reduction in energy intake, the higher is the fat loss. Fasting is the most effective way to lose weight. Major restriction in choice of foods lead to reduction in energy intake due to sensory-specific satiety (hedonic adaptation). Dieting and weight loss cause increased appetite and hunger, being the biggest problem after a diet (that's why we put back the weight) and we need to mentally prepare and use our will until balance is reached once more (you need to give your body time to adapt). A high protein diet promotes satiety and is the most effective solution to suppress the hunger feeling. The improvement in health parameters after weight loss are determined by the amount of fat lost and not by the method used to lose weight. Long term success rate of weight lose is 10%, and people dieting ultimately fail and regain back the weight and even add some more.

Dietary fat and weight maintenance reached a peak in the Eighties, targeting fat intake to achieve weight lose because of the higher caloric density (9 kcal as opposed to 4 kcal for carbohydrates and protein). Fat was branded evil, but they ignored the importance of the daily total amount of calories (a positive energy balance with a lower percentage of fat intake will still make us to gain weight). As the fat-free meals consumption increased, with them still having loads of carbohydrates, later they started to brand carbs as being bad and they started to eat the good fats, once again ignoring the calories. There is no miracle pill or miracle food, if you keep a positive energy balance. No herbal tea, no lemon, no sauna belt, if it is too good to be true, it is a scam.

Physical exercise is an alternative or complementary approach to lose weight. The results tend to be lower than predicted as we partially compensate for the increased energy expediture by eating a bit more. Exercise done long enough helps to maintain weight, but physical exercise works slowly over time, while diet effects are shown faster.

Changing the obesogenic environment is another option. At least 30% of the global population is overweight or obese, all this increasing the chances of diabetes, heart diseases and cancer. Obesity related drugs are interfering with the appetite and food regulation (these processes are very centrally regulated, in some parts of the brain), leading often to unexpected side effects. There are locally active versions such as Lipase inhibitors (gastro-intestinal region), but they have limited effect and less side effects. Drugs development and research is not the answer (they are very expensive solutions).

We got the bariatric surgery, which is good and effective, but it is also very expensive and require lifetime supervision. If you often heard that obese people are to be held accountable for their problem, keep in mind that this is a myth, as much untrue as the idea that poverty can be avoided if you work harder. There are viable solutions, but obese people need extensive support. Obesity is a normal response to an abnormal environment (we are talking about food factors, socio-economic factors, cultural factors and much more). Add the genetic factors to all those external ones to complicate it even more. Obesogenic environments are conducive to obesity, and differences were observed between countries, even cities or neighborhoods. We have the Amsterdam example, where there are neighborhoods with less than 10% obesity and neighborhoods with more than 30% obesity. Even more, 75% of the obese children live in 2-3 neighborhoods out of 15. They are unequally distributed, , with lots of traffic, little opportunities of physical activity, unhealthy food at schools or promoted by intense marketing. The tendency to obesity starts early in life, degrees of obesity can be seen at 5 months already.

Possible solutions to deal with this are dual: micro-environments like schools, homes and neighborhoods oriented healthy lifestyles, macro-environments where price of the healthy food is acceptable, education systems and nation-wide supported programs (to teach how to eat less and exercise more - creating opportunities to be physically active and to have available and atractive healthy choices of food.

Short term interventions based on individual advice are not very effective, as they work on short term and then relapse. Long term interventions and strategies as the one aiming to drink more water did not work either, even after removing vending machines from schools, because 85% of sugary drinks come from home. The education of the family could be the key. One of the most effective strategy is to educate for the first 1000 days of life, young parents education combined with information refresher session periodically as starting early and taking a lifetime approach seems to be the best option.

Lasting lifestyle changes are extremely difficult for everyone, and the people with excess body-fat are not an exception. Even if you know very well what to do, in order to change your lifestyle and adopt a healthy eating with better activity patterns, you need to learn how to get rid of the bad habit and how to create a lasting good habit. I would mention here Charles Duhigg's book "The power of habit". Most of the cases, the changes in food intake and activity level are not sustained long enough to achieve the desired effects. Because of that, many of them turn to medical professionals for advice. Obesity as a health problem is a potential source of revenue for drug industry, and drugs come and go, full of promises, but no solution was found to truly work. Combined with lifestyle changes, they offer limited help, shredding of up to 10% of the body weight. Most of them work by curbing appetite and hunger, but they usually got many side effects, the damage done outweighing the benefits. You cannot expect to specifically reduce food intake without affecting many other processes of the human body.

The overall limited effectiveness of the weight loss drugs will introduce the possibility of bariatric surgery to us. What is that, you will ask? Bariatric surgery means the removal of parts of stomach and small intestine to induce weight loss. This is a very popular option lately, it is hugely effective in weight loss and as a side effect of solving the obesity issue, many diseases associated with it are ameliorated or even cured. Mortality due to obesity is dramatically decreased after bariatric surgery, and, even if we do not know really well how it is working, we believe that excessive stretching of the stomach leads to early satiety and reduced meal size. Defective food absorption is of minor importance, but we have changes in the release of certain hormones related to food intake and changes in taste sensation. We can see immediate improvements in health parameters such as blood glucose levels even before the weight loss. The general agreement is that the sudden negative balance is the main mechanism responsible for the rapid changes in metabolism. However, it should not be recommended and used only as a last resort for those facing immediate health risk and for who the other less invasive options have failed. They need to be carefully assessed as bariatric surgery can fail if is not used in conjunction with healthy lifestyle changes. Also, it is ineffective for people suffering from some underlying psychological disorder that caused obesity as a side effect. In order for bariatric surgery to succeed, the patient needs to receive dietary counseling before and after the surgery, and to learn and use an effective strategy combining diet with exercise.

Next and last post of this section will be about nutrition and sport.
Have a nice day!

G.

Causes of obesity

Causes of obesity are important to know and avoid, in order to achieve perfect health.

1. Overeating - the positive energy balance for an extended period of time, combined with a strong tendency among obese individuals to under-report their food intake or to underestimate the energy intake. In order to understand overeating, we need to study the factors leading to this. They can be psychological, social, environmental and genetic factors.

Psychological - we are talking about comfort eating or emotional eating, when eating temporarily take away the negative emotion (anger, stress, loneliness). Overeating will lead to guilt and extra-stress, which will create a vicious cycle leading to emotional or comfort eating. Smelling or seeing food increase impulsivity, increasing tendency to attend food cues, those are external factors which are extremely difficult to avoid, there is no single strategy to work for every problem, and the search and resolve are found individually.

Environmental factors - we are living in an obesogenic environment, with easy access to unhealthy food. Just think about the cinema pressure of watching a movie with popcorn and soda, or a memorable event leading to dining out and having that double fudge brownie gellato with mini marshmallows. Christmas and other major holidays are becoming a contest to create lost of expensive, over the top meals. The industrial processing is increased, we have less natural farming, we improve food shelf life by adding salt, sugar, chemicals or removing dietary fibers. Certain dietary habits lead slowly to a positive energy balance (higher usage of sugar, alcoholic drinks, high fat/high sugar meals known as energy dense meals, low fiber intake, low fruit and veg consumption, not having a proper time schedule of our meals). Add to this your sedentary lifestyle (work behind a desk, car use, watching TV or computer play for long intervals of time, car used to take children to school instead of walking or bike, online shopping instead of going the the physical place to buy it, even electric toothbrushes). Some people started to exercise to offset the decrease in energy expediture, but the ones needing it the most are the one less likely inclined to change their lifestyle and do more exercise.

Genetic factors (Thanks God for twin studies) - the genetic influence is larger than you think, even larger than some external factors, and after overfeeding and underfeeding trials, researchers observed that it is important to know how much fat we store and where we store it. Leptin hormone, as we learned already in previous posts, increase when we are fasting, creating a sensation of hunger, There are some rare cases where the leptin is absent (MC4A inactive gene), and the individual is always hungry. We are talking about 5% of all the obesity cases that exists due to this mutation. People with unfavorable genetics are more prone to overeat and environmental factors explain the overall increase in obesity prevalence, while the genetic factors explain the inter-individual differences.

But you need to know that heritability is not destiny, and can be improved by adopting healthy habits. Creating habits that are long lasting is a skill and can be improved through learning. 

Next post: possible solutions for obesity.

Body fat distribution and the health risks of obesity.

Excess body fat is stored at multiple sites in the human body. Most of it is stored under the skin in the form of subcutaneous fat. A small quantity is located in the abdominal cavity connected to pancreas, intestine and other organs. This is called visceral or intra-abdominal fat, and it is adding more risks to the health than the subcutaneous fat. People with high amount of visceral fat have a large waist (central or abdominal obesity) and and apple shaped body. People with high subcutaneous fat on the buttocks or legs have a pear shaped body. Waist fat pinched during measurements is subcutaneous fat. A proper estimation of visceral and subcutaneous fat is done via MRI (magnetic resonance imaging). A cross sectional image made at the abdominal level will make possible to visualize the different fat depots and calculate visceral/subcutaneous fat surface area. But for the ones without the technical availability of MRI, the amount of visceral fat is relatively well correlated with the waist circumference and/or waist to hip ratio. Obesity rates are different between countries (geographic areas). The highest obesity rates are recorded in the Pacific Islands area, due to an energy rich diet and genetic predisposition towards obesity (US and Australia included). Lower obesity rates are recorder in most European, African and Asian countries, with Ethiopia and Eritrea being the lowest.

When BMI is higher than 30, which translate by being obese, the mortality risk increase, with problems such as cardio-vascular diseases, stroke, sleep apnoea, diabetes, lung disease, liver and pancreas problems and even cancer risk also increasing. The metabolic syndrome is characterized by abdominal obesity, hypertension, elevated blood cholesterol and triglycerides increased, insulin resistance (pre-condition of type 2 diabetes) and a higher chance of heightened inflammatory state and blood clotting. Type 2 diabetes is often associated with obesity, but the loss of body fat cause immediate improvement of this condition. Increases in fat mass causes the fat tissue to become inflamed (state of chronic low grade inflammation). Obesity increase the tendency of the blood to clot, which is another important risk.

Next post: causes of obesity.

Have a nice day!
G.

Weight management and obesity measurement

We will talk first about BMI (body mass index), which can be calculated dividing weight in kg by height in meters squared. If i have 84 kg and 1.78 m, then my BMI will be 84/(1.78 x 1.78) = 26.51. Between 20-25 you are good, 25-30 overweight, 30-40 obese, over 40 morbidly obese. The only problem is that this method will not take in account your body composition, so if you are an athlete with well developed muscles, according to this method you can be classified overweight. BMI disregards the body fat distribution, which can be useful to show heart risks.

Other more accurate method is the Fatfold or Skinfold method. This one measure the thickness of the skin (including the underlying subcutaneous fat layer) using a Skinfold caliper. We measure front tight, upper back, waist and upper arm. There is a strong correlation between the thickness of the subcutaneous fat layer and the total amount of the body fat.

There are some exotic techniques such as Hydrodensiometry (underwater weighting) and Air Displacement Plethysmography, which both measure the density of the body, dividing body mass by body volume. Body density can be used to compute body fat percentage using a mathematical formula (assuming fat density is 0.9 and lean body mass is 1.1 as constants). The idea behind this is that obese people with low body density will float in water and lean people with high body density will sink more in water.

Other way is by using Bio-electrical Impedance, sending tiny electrical impulses through the body and measuring the return of impulses, as lean tissue conducts electrical impulses more easily than fat tissue. This method is now affordable, easy to use, but not very accurate.

DEXA (Dual Engage X-ray Absorptiometry) is a method that uses x-ray to determine body composition (including details like done density). It is very accurate, very expensive and has small risks due to irradiation.

Non-obese males value is 10-20% body fat, non-obese females 20-30% body fat. As we age the body fat increases as we replace muscle with fat.