There is without a doubt conventional wisdom about metabolism. It goes something like, “Most people gain weight each year no matter what because their metabolisms slow down, especially around middle age.”.
We’ve also been told that women have slower metabolisms than men. Menopause only makes things worse, slowing women’s metabolisms even more.
Turns out, none of this is true.

A study done a few year ago, published in Science, using data from 6,400 people across the world, ranging in age from 8 days to 95 years old, had some results that have changed how experts think about metabolism.
The shocking results of this study were made possible because they were able to use regression analysis to remove any excess body fat from each person. Not only did they find that there are no real differences between the metabolic rates of men and women after controlling for other factors, but the results also showed something that had never been identified - four distinct phases of human metabolism based on age.

The four phases of metabolism:

    Infancy (Up to 1 year): Metabolism is at its highest, burning calories at a rate about 50% higher than adults. Babies absorb everything. Everyone loves a fat baby, right?

    Adolescence (1 to 20 years): The metabolic rate gradually slows by about 3% each year until it reaches adult levels around age 20. Despite the teen years being a time of growth spurts, the researchers didn’t see any uptick in daily calorie needs in adolescence after they took body size into account.

    Adulthood (20 to 60 years): The metabolic rate remains stable, even through major hormonal changes like pregnancy and menopause. We are hardwired for our metabolism to be stable through the majority of our adult life. While several factors could explain the thickening waistlines that often emerge during our prime working years, the findings suggest that a changing metabolism isn’t one of them.

    Older Adulthood (After 60 years): The metabolic rate begins to decline, slowing by about 0.7% to 1% per year. This decline is likely linked to a general slowdown in organ function. Energy requirements of just the heart, liver, kidney and brain account for about 65% of your resting metabolic rate.  The slowing of your metabolism at age 60 is likely then linked to your organs not functioning as well as they should.  The authors go so far as to note that despite how ‘young’ a person looks in their 60’s, biologically their organs are likely not functioning nearly as well as they had previously. Getting old is just never going to be easy on your body!

There are more than 80 co-authors on the study. They combined data from six different labs collected over 40 years. All of the research centers involved in the project were studying metabolic rates with a method considered the gold standard — doubly labeled water. It’s a urine test that involves having a person drink water in which the hydrogen and oxygen in the water molecules have been replaced with naturally occurring “heavy” forms and then measuring how quickly they’re flushed out. The investigators also had participants’ heights and weights and percentage body fat, which allowed them to ultimately factor in someone’s excess fat and muscle mass when it came to calculating their actual metabolism.

Many people still see their weight increase as they get older, despite their metabolism staying relatively the same throughout their life. This suggests that weight gain isn’t a result of slowing metabolism. Rather, it’s more likely to be due to eating more food than our body uses. What else contributes to weight gain?

Primary factors to weight gain as we age are:

Muscle loss (Sarcopenia): Starting around age 30, adults lose about 3–8% of muscle mass per decade. Muscle burns more calories at rest than fat, so less muscle mass means fewer calories are burned throughout the day.

Reduced physical activity: People tend to become less active as they get older, which lowers overall daily energy expenditure. They usually do not adjust food intake accordingly.

Poor sleep: Your body continues to perform essential functions overnight, requiring energy (45-55 calories per hour) to do so. This includes repairing cells, processing nutrients, and maintaining a core body temperature.

Fat storage: Excess body fat crushes our metabolism. The body's ability to burn fat for energy is reduced, while its capacity to store fat increases, creating a cycle that favors further weight gain

Medications: Some medications can promote weight gain.

Remember that all of these findings were after controlling for the amount of fat free mass people have - pretending people were all lean - and then comparing.  

The study shows that less fat that you have, regardless of age, the more energy you expend. 

Before we dig into it's safety, let's go back in time. Why is fluoride in our water anyway?

It all goes back over 120 years to 1901, when a young dental school graduate named Frederick McKay left the East Coast to open a dental practice in Colorado Springs, Colorado. When he arrived, he found the people of Colorado Springs with brown stains on their teeth. To his surprise, the teeth afflicted by brown stains were somehow more resistant to decay than those he had seen back home.

Years later, while studying this brown stains, McKay and Dr. Grover Kempf of the United States Public Health Service (PHS) traveled to Bauxite, Arkansas. This small town was home to Aluminum Company of America (ALCOA), which mined the ore found in the ground there and built plants and mills to process this bauxite ore that is a key component in aluminum. In this town, the two men discovered that the same brown enamel disorder was prevalent among the children of Bauxite, but nonexistent in another town only five miles away.

McKay and Kempf published a report on their findings that reached the desk of ALCOA's chief chemist, H. V. Churchill. He then decided to conduct a test of the water in Bauxite, which found that the town's water had high levels of fluoride.

In January 1931, Churchill wrote a letter to McKay regarding his findings. In the letter, he advised McKay to collect water samples from other towns "where the peculiar dental trouble has been experienced. We trust that we have awakened your interest in this subject and that we may cooperate in an attempt to discover what part 'fluorine' may play in the matter."

McKay collected the samples. And, within months, he had the answer to his 30-year quest. High levels of water-borne fluoride indeed caused the discoloration of tooth enamel. It just so happened that fluoride was naturally present in the groundwater in all of these locations. It occurs due to the dissolution of fluoride-rich minerals in rocks and soil.

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Add it to the tap water.

Fourteen years later, in 1945, Grand Rapids, Michigan became the first city in the world to purposely fluoridate its drinking water, at an amount high enough to reduce decay, but low enough to prevent the brown stains. The Grand Rapids water fluoridation study was originally sponsored by the U.S. Surgeon General but was taken over by the NIDR (National Institute of Dental and Craniofacial Research) shortly after the Institute's inception in 1948. During the 15-year project, researchers monitored the rate of tooth decay among Grand Rapids' almost 30,000 schoolchildren. After just 11 years, the caries rate (tooth decay) among Grand Rapids children born after fluoride was added to the water supply dropped more than 60%. This finding, considering the thousands of participants in the study, amounted to a giant scientific breakthrough.

Today, just about every toothpaste on the market contains fluoride as its active ingredient and approximately 73% of the U.S. population on community water systems receives fluoridated water.
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But is it safe?

Robert F. Kennedy Jr. is now the Secretary of Human and Health Services in the United States. He is outspoken about the potential harms of fluoride. Earlier this year, he stated “Fluoride is an industrial waste associated with arthritis, bone fractures, bone cancer, IQ loss, neurodevelopmental disorders, and thyroid disease.” These statements are getting a lot of press and so I wanted to dive into the issue.

There is a recent history of research leading to a universal change in fluoride in drinking water. In 2015, the U.S. Public Health Service (PHS) updated its recommendations for fluoride levels in community water systems.

The decision was based on several factors, including the widespread availability of fluoride in oral care products and other sources and the observation that children were experiencing dental fluorosis (white splotches on teeth) due to excessive fluoride exposure.

The new recommendation set a uniform concentration of 0.7 mg/L (or 0.7 ppm) of fluoride in drinking water. This change aimed to ensure that while cavity prevention benefits were maintained, the risk of dental fluorosis in children was also minimized.
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But even if it protects your teeth, can fluoride be doing damage to other parts of your body?

There have been several studies over the last 30 years that found fluoride could cause brain damage, but only at extreme levels – much higher than we find in water. There was also a study just last year showing that higher levels of fluoride in pregnant women’s urine showed double the odds that their children have neuro-behavioral problems by age three. There were eight other studies that looked into this same phenomena and six of them found similar results. Other studies show that those that grew up with fluorinated water showed no significant differences in IQ from those that did not. The data is all over the place.

There is also a little evidence that fluorine can cause hyperthyroidism and increase risks of bone fractures, but nothing conclusive.

Based on what I can find, there is no strong evidence or Meta Analysis that definitively says that there are dangers to drinking water with fluoride.
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But it’s still good for dental health, right?

There have been several cities that have removed fluoride from their drinking water and it is documented that kids that have grown up without fluorinated water will have around 10% more cavities. If you are already an adult, the benefits don’t appear to be as great. Permanent teeth have a thicker enamel and adults also tend to be better at brushing and flossing.

Outside of drinking water there are other sources of fluoride that we encounter. Black tea and coffee can be significant sources of fluoride. As well as seafood like crab, shrimp, and fish. Unfortunately, pesticides contain fluoride, so non-organic fruits and vegetables may also contain it. Could some of these other sources be contributing to the findings of the studies showing a link to neurological issues, hyperthyroidism and increased risks of bone fractures? Possibly.

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So what's the conclusion? There is none.

Research on this topic needs to be continued and if someone is telling you the results are conclusive in one way or the other, they likely have an agenda.

As for me and my family, we stopped buying fluoride toothpaste for our home years ago, but I still drink tap water – which here in Louisville, typically contains an average of 0.6-0.7 ppm of fluoride according to the Louisville Water Company’s website. My rational is that we are exposed to enough fluoride already and we all visit the dentist regularly. If there is a link to any dangers around fluoride consumption, taking this one source away seemed to be worth it to me.

Kelly Anne Hyndman, a kidney function researcher at the University of Alabama at Birmingham will tell you that staying hydrated is definitely important, but the idea that the simple act of drinking more water will make people healthier isn’t true. Nor is it correct that most people are walking around chronically dehydrated or that we should be drinking water all day long.

We’ve probably all heard that eight, 8-ounce glasses of water per day is the magic number for everyone, but that notion is a myth according to Tamara Hew-Butler, an exercise and sports scientist at Wayne State University. If you are reading this on my website, then you’ve undoubtedly heard me say that there is never “one size fits all” for anything. Water consumption is no different. Unique factors like body size, outdoor temperature and how hard you’re breathing, and sweating will determine how much water you need.

A 200-pound person who just ran 6 miles of trails in the heat (like I did as part of a Ragnar relay race this past weekend), will obviously need to drink more water than a 120-pound person who spent the day in a temperature-controlled building.

The amount of water you need in a day will also depend on your health. Someone with a medical condition like heart failure or kidney stones may require a different amount. Or you may need to alter your intake if you’ve been ill, with vomiting or diarrhea.

For most people, the best way to stay hydrated is simply to drink when you’re thirsty. This goes for anyone that is healthy. This method should be used at all times. While exercising and while sitting at a desk. The term “Drink to Thirst” is one that I heard over 10 years ago from Tim Noakes and is a motto I repeat to myself often. A study in 2018 confirmed that “it would appear that conditions exist where ad libitum/drink to thirst fluid intake will be sufficient to meet needs.”

And despite popular belief, don’t rely on urine color to accurately indicate your hydration status. While it’s possible that dark yellow or amber urine could mean that you’re dehydrated, there’s no solid science to suggest that the color, alone, should prompt a drink.

While most people have never tried to rely on listening to their body when it comes to thirst, it’s a good idea to start. The notion that staying hydrated requires complex calculations and instantaneous adjusting to avoid dire health consequences is just bunk, the experts said. And one of the best things you can do is to stop overthinking it. Getting in tune with your body has many benefits and paying attention to how thirsty you are is a good way to start this practice.

What about electrolytes?

Gatorade and Powerade might have you thinking you need to constantly be replenishing electrolytes to keep their levels in check, but there’s no scientific reason for most healthy people to drink beverages with electrolytes according to Dr. Hew-Butler.

Electrolytes like sodium, potassium, chloride and magnesium are electrically charged minerals that are present in the body’s fluids (like the blood and urine) and are important for balancing the water in your body. They’re also essential for proper functioning of the nerves, muscles, brain and heart.

Most people get enough electrolytes to sustain bodily functions from food. So unless you are exercising and sweating excessively, don’t even worry about electrolytes.

If you are exercising and are losing electrolytes, look for non-sports drink options. Sports drinks do contain electrolytes like sodium and potassium which are lost through sweat, but they are often higher in sugar and calories than soda! Healthier alternatives like infused water combinations, watermelon juice, and coconut water are options that I have successfully used before. Just look for added sugars on the label.

I’m not going to waste your time or mine giving you the history of the COVID-19 virus and the ensuing pandemic. Everyone has lived through the last 5-6 months and has their own opinions on where and how it originated and spread throughout the world. I see your posts on social media, I know all the theories.

Early on in the outbreak, evidence out of China showed that there was a connection between the virus and pre-existing conditions.

The Center for Disease Control (CDC) website even states that some people are at higher risk than others when it comes to COVID-19. It specifically lists people over 65 and people of all ages with underlying medical conditions, particularly if not well controlled, including:

• People with chronic lung disease or moderate to severe asthma
• People who have serious heart conditions
• People who are immunocompromised
• Many conditions can cause a person to be immunocompromised, including cancer treatment, smoking, bone marrow or organ transplantation, immune deficiencies, poorly controlled HIV or AIDS, and prolonged use of corticosteroids and other immune weakening medications
• People with severe obesity (body mass index [BMI] of 40 or higher)
• People with diabetes
• People with chronic kidney disease undergoing dialysis
• People with liver disease

Many of these conditions are caused by excess body fat; or a term that is starting to be more widely used, called overfat. The overfat condition itself is a significant yet little discussed risk factor in infectious viral diseases, with overfat negatively affecting immune function.

In addition to food, you can help your immune system function as designed by flushing your system regularly with lots of water and getting plenty of rest. Just as important, the strength of your immune system is also directly linked to how you manage stress, how you manage your relationships and past traumas.

If you make sacrifices and focus on improving your diet, sleep and stress, you may be astonished with the positive results - both those that you can see and those that you can’t (your immune system).

As we move into the summer and fall, we will discover a lot more about COVID-19. But as we sit here today unsure of how and when life should start to return to normal and the consequences of public interaction, I suggest that you focus on what you can control. Despite the way it seem, you have control over a lot more than you realize. Protect yourself, your family and those you come in contact with by using masks, social distancing and washing hands, but also take it one giant step forward by giving your immune system what it needs!