The mysterious virus that can cause obesity
Obesity doubtless has multiple causes, but some scientists are now focused on the possibility in some cases a virus could be at fault. The Secret Life of Fat: The Science Behind the Body’s Least Understood Organ and What It Means for You is a book by Sylvia Tara that discusses this. Wired magazine has an excerpt from that book:
RANDY IS 62 years old and stands tall at six foot one. He grew up on a farm in Glasford, Illinois, in the 1950s. Randy was raised with the strong discipline of a farming family. From the time he was five, he would get out of bed at dawn, and before breakfast he’d put on his boots and jeans to milk cows, lift hay, and clean the chicken coops. Day in and out, no matter the weather or how he felt, Randy did his physically demanding chores. Only when his work was complete would he come into the kitchen for breakfast.
Tending to the chickens was hard work—it involved getting into the pen, clearing birds out of their dirty cages, and shooing them into a holding enclosure. This process was always a little scary because the animals could be quite aggressive after being cooped up all night. On one of these occasions, when Randy was 11, a particularly large and perturbed rooster swung its claw and gave him a good spurring on his leg. Randy felt the piercing of his skin and squealed in pain. He said it felt like being gored by a thick fishhook. The rooster left a long gash, and blood streamed down Randy’s leg to his ankle. He ran back to the house to clean the wound, as chickens are filthy after a night in their cages.
Some days later, Randy noticed a change in his appetite. He was constantly hungry. He felt drawn to food and thought about it all the time. He started eating in between meals and overeating when he finally sat down to dinner. Randy had always been a skinny kid, but in the course of the next year, he gained about 10 pounds. His parents thought it might be puberty, though it seemed a little early. His pudginess was also unusual given that everyone else in the family was thin. Randy was no stranger to discipline. He forced himself to eat less, switched to lower-calorie foods and exercised more. But by the time he was a teenager, he was bouncing between 30 and 40 pounds overweight. He says, “I gained all of this weight even though these were some of my most active years on the farm.”
Randy’s family supported his efforts to control his weight. They made lower-calorie foods, gave him time to exercise, and didn’t pressure him to eat things he didn’t want. However, he continued to struggle with his weight through college. Randy kept thinking back to the moment everything changed. He had been the skinniest kid among his friends. And then he got cut by that chicken.
The Curious Case of Indian Chickens
In Mumbai, India, Nikhil Dhurandhar followed his father Vinod’s footsteps in treating obesity. But Nikhil ran into the same obstacle that had bedeviled obesity doctors everywhere. “The problem was that I was not able to produce something for patients that could have meaningful weight loss that was sustainable for a long time,” he says. “Patients kept coming back.”
Fate intervened in Dhurandhar’s life one day was when he was meeting his father and a family friend, S. M. Ajinkya, a veterinary pathologist, for tea. Ajinkya described an epidemic then blazing through the Indian poultry industry killing thousands of chickens. He had identified the virus and named it using, in part, his own initials—SMAM-1. Upon necropsy, Ajinkya explained, the chickens were found to have shrunken thymuses, enlarged kidneys and livers, and fat deposited in the abdomen. Dhurandhar thought this was unusual because typically viruses cause weight loss, not gain. Ajinkya was about to go on, but Dhurandhar stopped him: “You just said something that doesn’t sound right to me. You said that the chickens had a lot of fat in their abdomen. Is it possible that the virus was making them fat?”
Ajinkya answered honestly, “I don’t know,” and urged Dhurandhar to study the question. That fateful conversation set Dhurandhar on a path to investigate as part of his PhD project whether a virus could cause fat.
Dhurandhar pushed ahead and arranged an experiment using 20 healthy chickens. He infected half of them with SMAM-1 and left the other half uninfected. During the experiment, both groups of chickens consumed the same amount of food. By the end of the experiment, only the chickens infected with the SMAM-1 virus had become fat. However, even though the infected chickens were fatter, they had lower cholesterol and triglyceride levels in their blood than the uninfected birds. “It was quite paradoxical,” Dhurandhar remembers, “because if you have a fatter chicken, you would expect them to have greater cholesterol and circulating triglycerides, but instead those levels went in the wrong direction.”
To confirm the results, he set up a repeat experiment, this time using 100 chickens. Again, only the chickens with the SMAM-1 virus in their blood became fat. Dhurandhar was intrigued. A virus, it seemed, was causing obesity. Dhurandhar thought of a way to test this. He arranged three groups of chickens in separate cages: one group that was not infected, a second group that was infected with the virus, and a third group that caged infected and uninfected chickens together. Within three weeks, the uninfected chickens that shared a cage with infected ones had caught the virus and gained a significant amount of body fat compared to the isolated uninfected birds.
Fat, it seemed, could indeed be contagious.
Now, Dhurandhar is a man of science. He is rational and calm. But even he had to admit that the idea was startling. Does this mean that sneezing on somebody can transmit obesity? This now seemed possible in animals, but what about humans? Injecting the virus into people would be unethical, but Dhurandhar did have a way to test patients to see if they had contracted the virus in the past.
Dhurandhar says, “At that time I had my obesity clinic, and I was doing blood tests for patients for their treatment. I thought I might just as well take a little bit of blood and test for antibodies to SMAM-1. Antibodies would indicate whether the patient was infected in the past with SMAM-1. The conventional wisdom is that an adenovirus for chickens does not infect humans, but I decided to check anyway. It turned out that 20 percent of the people we tested were positive for antibodies for SMAM-1. And those 20 percent were heavier, had greater body mass index and lower cholesterol and lower triglycerides compared to the antibody-negative individuals, just as the chickens had.” Dhurandhar observed that people who had been infected with SMAM-1 were on average 33 pounds heavier than those who weren’t infected.
The Pounds Keep Coming
While Nikhil Dhurandhar was in India pursuing his curiosity about fat, Randy was looking for solutions of his own. After a brief stint as a teacher he moved back to the family land in 1977 because he loved farming.
Randy married and had four children. At family dinners and holiday gatherings, he ate alongside everyone else, but tried eating less than the others. Still, his weight ballooned; by his late 30s he had topped 300 pounds. He remembers feeling hungry all the time, though even when he abstained it didn’t help him lose weight. “I could have several good weeks of eating stringently, much less than others around me, but if I went off my diet for just one meal—boom, the weight would come back.”
The effort to control his eating, even when it was successful, made Randy miserable: “I can’t tell you what it is like to be hungry all the time. It is an ongoing stress. Try it. Most people who give advice don’t have to feel it.”
In the fall of 1989, Randy applied for a commercial driver’s license. The application required a medical exam. After his urine test, the nurse asked Randy if he felt all right. “Normal for the day,” he replied. But the nurse told Randy he would have to give a blood sample because she thought the lab had spilled glucose solution into his urine sample. The blood work showed that Randy’s glucose level was near 500 mg/dL (a normal reading is 100). The lab hadn’t made a mistake with the urine sample after all; Randy’s numbers were just off the charts. Alarmed, the nurse notified Randy’s doctor, who then tested him for fasting blood sugar levels. The results showed that Randy had insulin resistance and severe diabetes.
At 40 years old and 350 pounds, Randy was in trouble. If he didn’t fix this problem soon, he would start to develop serious complications of diabetes, including cardiovascular disease and nerve damage.
Having tried and failed multiple diets, Randy and his doctor decided the best hope was . . .