Why is Losing Weight Harder When We are Older?

University of California researchers explore how fasting and the keto diet can help.

The question that perplexes many older adults and keeps them on treadmills and one diet after another is this one: Why is weight loss more difficult as we age?

“Lots of reasons: As we age, what we eat changes; how we live changes and because we tend to become less active, our body metabolism changes. We need less energy because our bodies use less energy to repair and rejuvenate,’’ said Dr. John Newman, geriatrician and researcher at the Buck Institute for Research on Aging at University of California San Francisco (UCSF) Department of Medicine. “So, we must constantly adjust how we live.’’

Newman was one of three panelists who spoke recently during a virtual discussion, “Weight, Metabolism and Aging: The Science Behind Fasting and Keto,’’ presented by the American Federation for Aging Research in New York. The panel also included Dr. Satchin Panda, a researcher into circadian rhythms and time-restricted eating at the Salk institute for Biological Studies, La Jolla, Calif., and moderator Sarah Smith, editor in chief of Prevention magazine.

“The key is to eat a small amount of carbohydrates and to eat healthy fats, which are found in the Mediterranean style diet: fish, avocados, olive oil. That should be the core of the ketogenic diet,’’ Newman said.

Although the ketogenic diet, or keto, resembles the Mediterranean diet, there are major differences. In particular, keto aims to bring down carbohydrates to less than 5% of intake. The Mediterranean diet focuses on plant-based eating but doesn’t emphasize reducing carbs — the diet allows for foods that are (but aren’t always) high in carbs, such as bread, grains, fruits, vegetables and even some sweets. Which diet works better has been the subject of discussion and controversy. The keto diet has gained popularity in recent years, particularly among a number of celebrities. Studies have shown it can control
inflammation, as well as produce significant weight loss. Other researchers at UCSF have also studied the keto diet and how it works.

Newman noted during the AFAR panel discussion that the slowed metabolism that people experience with age has been shown to cause problems such as dementia and delirium. The ketogenic and Mediterranean-style diets help bolster brain health by countering the effects of a slowed metabolism, he said.

“Studies show that most adults aged 50+ have some pain in their joints and muscles, and one-third to one half of older adults take pills for high blood pressure or blood sugar. Unfortunately, many pills have the side effect of weight gain because they cause fluid retention and that makes it even harder to lose or maintain weight,’’ said Panda, author of “The Circadian Code: Lose Weight, Supercharge Your Energy and Sleep Well Every Night.’’

“The good news is that we can make small changes in our diet and sleep and even if we don’t always lose weight, we can become healthier,’’ Panda added.

Newman said clinical trials on the ketogenic diet show that it resembles the Mediterranean style diet and is a good choice to maintain heart, brain and body health.

Researchers have traced the long and healthy lives of Greek and Southern Italians living on the Mediterranean Sea to their diet, which lowers blood sugar and insulin levels and helps the body metabolize fat and ketones.

So what are ketones? Ketone bodies or ketones are the water-soluble molecules produced by the liver from fatty acids when there is low food intake (fasting) or carbohydrate restriction. When insulin levels are low, the body is unable to use sugar (glucose) for energy, so it breaks down its own fat and protein, releasing these acids from the liver into the bloodstream, where they are used as fuel.

Fasting, Panda said, “helps the body reset, repair itself, rejuvenate and age slower. Over time, fasting can help reduce the occurrence of diabetes, and it can lower high cholesterol and high blood sugar,’’ he said.

During sleep, our bodies fast naturally, Panda said; this is what’s known as time-restricted eating or intermittent fasting. He said the last food of the day should be eaten at least three hours before sleep, and that at least seven hours of sleep nightly is healthy. He recommends at least eight and up to 12 hours of daily intermittent fasting.

“For health benefits, you must do this (time-restricted eating) every day or at least five days a week, and aim to go to sleep at around the same time every night,’’ Panda said.

Despite misconceptions about the role and value of ketone bodies, Newman said they are essential. “They are a normal part of our body and they help us get through everyday life. They metabolize fat for fuel; fat goes from the liver to the heart to muscles and the brain. We don’t make a lot of ketone bodies when we are eating but our body makes a lot more when we are fasting. The [keto] diet is a way of tricking the body into making more ketone bodies,’’ Newman said.

Panda said the body reacts differently to fats and protein versus carbohydrates when converting them into fuel and making ketone bodies. “During fasting, the body breaks down fats to make ketone bodies. In the last hour (of sleep) the body is making a lot of ketone bodies. But if we eat too much carbohydrates, there is a lag time to get rid of them and then to make ketone bodies.’’

To counteract this, Panda said, change your habits. “Most bad habits happen at night — alcohol and snacks and unhealthy desserts. Pay attention to reducing alcohol and reducing sugar,’’ Panda said.

The effect of the ketogenic diet on laboratory mice indicates that humans might not have to adhere to  the diet every day. “The science says maybe not. So, would mice on the occasional ketogenic diet be  healthier and live longer? Yes!’’ Newman said. “The mice were only fed the ketogenic diet half the time.

Even when they were not eating the diet, they had healthier brains. The biology of ketone bodies is that they might stick around so it might not have to be “all or nothing at all,’’’ he said.

Human participants in ketone bodies research experiments that were 16 weeks to one year long were revisited after the year; some participants said they continued on the regimen. Why?

“Because they said they felt more energetic and less hungry at bedtime,’’ Panda said. And just by doing time-restricted eating, Panda added, some participants saw a reduction in their blood pressure.

Is there is an ideal period for time-restricted eating? “Most important is to consider your lifestyle: It could be from 8 a.m. to 6 p.m., or noon to 10 p.m. Whatever you can do is better than (eating at) random times, Panda said.

Both doctors said check with your doctor first before embarking on a time-restricted regimen or ketogenic diet, especially those who take medicine. “We want people to not be afraid of the (diet), but because of changes that could take place in the body’s metabolic state you need to talk to your doctor  first. For instance, if you lower your blood sugar, you might have to have your medicine adjusted,’’ Panda said.

Newman added the effects of the diet on heart health are unknown. “Most diets don’t have decades-long data on heart health, which is true of the ketogenic diet. We’re still continuing to study the effects,’’ Newman said.

In a four-decade career in journalism, Eleanor O’Sullivan has reviewed many books on best practices for financial advisors, has written for Financial Advisor and the USA Today network, and was movie critic for the Asbury Park Press.

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