Diet drinks containing sugar substitutes were found to be as effective as water for supporting weight loss in overweight or obese adults, according to a two-year randomized trial.
The study, led by the University of Liverpool, England, included 493 participants ranging from 18 to 65 years old, all of whom had a body mass index (BMI) between 27 and 35 (overweight or obese).
Half of them received 22.3 ounces of water each day, and the other half received the same amount of soda with non-nutritive sweeteners (about two cans) for a 104-week period.
The group assigned to NNS drinks could choose from a variety of diet sodas, low-calorie fruit drinks and flavored waters. The primary sweeteners used were aspartame, acesulfame potassium and sucralose.
After two years, people drinking diet beverages had lost about 10.6 pounds, while those drinking water lost about 8.2 pounds.
People in both groups kept off a meaningful amount of weight for two years, even during the last year when they no longer had regular weight-management support, the researchers stated.
Both groups lost inches around their waists and hips and reduced body fat, but there was no meaningful difference between people drinking diet beverages and those drinking water.
Additionally, total cholesterol remained within the healthy range in both groups.
The findings were published in the British Journal of Nutrition.
“The study does not show that diet beverages themselves caused the weight loss,” Alix Turoff, a registered dietitian in New York City, told Fox News Digital.
“Everyone in the study was participating in a structured weight-management program that included nutrition counseling, behavioral support and physical activity recommendations.”
Turoff, who was not involved in the study, noted that the main value of including diet beverages comes down to substitution, “not that these beverages have a magical metabolic effect.”
Notably, the study compared diet beverages with water — rather than with sugar-sweetened drinks — making it a test of whether the sugar substitutes themselves appeared to hinder weight loss efforts.
“If someone normally drinks 250 calories of regular soda and switches to zero-calorie soda, then they’re saving calories,” she added.
The dietitian emphasized that these findings don’t mean water and diet soda are nutritionally identical.
“The study did not find significant between-group differences in hunger or sugar intake at the end of the trial, which is relevant because one common concern is that artificial sweeteners may increase appetite or lead to compensatory eating,” Turoff said.
“I would still recommend water as the primary hydration choice, but I don’t think people need to be afraid of diet drinks because they think they will automatically prevent fat loss or cause weight gain.”
There were some limitations with the research, including that it was conducted at one location in England. Race and ethnicity data were not collected, which limits the generalizability of the findings.
Only 220 of the 493 participants who started treatment completed the 104-week assessment. The second-year extension was also voluntary, meaning those who continued may have been more motivated or more likely to stick with the program, Turoff noted.

Each week, exclusively for Slate Plus members, Prudie discusses a new letter with a fellow Slate colleague. Have a question for Prudie? Submit it here.
Dear Prudence,
My husband has pretty severe anxiety/OCD, mostly concentrated on health and medical situations. Nothing can be a minor illness—it is a sign of something much more serious and sinister. He is on medication for it and he reports that it helps, but I do think he most likely needs a higher dosage or something for more support. He regularly (probably four times a year) becomes convinced he has an STI of some type due to relatively benign symptoms like a rashy dry skin patch or a bruise near his genitals. When this happens, he usually asks me a couple times if I think he could have (fill in the blank STI). I usually just ask if he’s had sex with anyone else or thinks I have, he says no, and I say “then I don’t see how you would have an STI” and refuse to answer him on it again (original advice of his doctor/counselor when starting OCD treatment).
But this last time has been different.
About one week after travelling for work, he asked again about what was definitely an eczema patch. I answered as I usually do, but a couple days later he told me he was really worried about it and was going to contact his doctor to order blood testing for STIs. I said I thought that was unnecessary. He got the tests done and everything was negative, so he went right back to his usual self.
But now I’m convinced he cheated on me on his work trip. Since starting his medication, he has never needed more than a verbal confirmation that he wouldn’t have an STI. I have never thought he would cheat on me, but he did go out with people one night, and I know they all drank quite a lot. When he travels, he normally calls me either before bed or in the morning while I’m getting ready for work and he didn’t this time, instead texting that he was out and then around lunchtime the next day saying it had been a rough night/morning. What would you recommend as the best way to approach him on this? I’m worried he’s going to just explain it away as his OCD being more severe this time and needing more reassurance, but I also think this is a reasonable reaction on my part. I feel like I’m always supporting him through the things he struggles with and the one time I have a concern (that actually has some evidence to it!), it’s just going to get brushed off.
—Now I’m Anxious
Jenée Desmond-Harris: I don’t know why I initially misread this as being about her brother (I truly pulled that out of nowhere) and I was so happy to say “You don’t have to worry about this! It’s not your business.” Now that I have my facts right, things have become a lot heavier. Yeah, this is totally her business.
Lizzie O’Leary: I am kind of stunned by the lack of trust here. And maybe that’s not fair, but it’s wild to be repeatedly asking your spouse if they have had sex with other people, even if most of that is coming from a place of mental illness! I think that is the place these two need to start.
Jenée: Right, if you’re going to have ideas about STIs that don’t have a basis in reality, you may as well take the irrational thinking all the way and imagine that you got them from a toilet seat or something.
I agree with you that the lack of trust is a big problem. And actually, it would be helpful for the letter writer to strip away all the mental health history and ideas about what kind of support she’s owed and how her husband will receive her concerns and focus on the core issue: She thinks her he cheated! And that he’ll lie about it! So maybe the goal is not to get him to take that concern seriously, but to decide what it means for whether she wants to be in this marriage.
Do you think a digital snooping investigation is warranted here? Because I know nobody wants to get divorced based on a weird feeling alone.
Lizzie: I think some counseling is warranted. Digital snooping is so messy, and even if she finds some proof of affair, getting it that way is horrible and upsetting. And puts her on the back foot. I think she needs to tell her spouse how she feels, AND that she is so turned around by all of this that she doesn’t know whether to trust him. It sucks, but I don’t think there is a way to be like “hmm yeah I think you may still be lying though,” without really probing what that means about the marriage.
Jenée: Well, I’m glad there’s one reasonable and mature person in this chat. I’m not sure why I suggested the 19-year-old approach. Counseling would be great because maybe things could be repaired (I know an Esther Perel or Dr. Orna wouldn’t see it as a dealbreaker even if the cheating allegations were confirmed—maybe there’s a better relationship on the other side of this!) and if not, it would be nice to have someone to guide the couple through wrapping things up. Oh, and maybe the therapist would suggest more individual work for the husband, which could lead to a medication adjustment, which could lead to STI worries no longer playing such a big role in this relationship.
Lizzie: Yeah, at the bare minimum, repeated allegations of cheating over random rashes are not a great way to live! Jenée, maybe if I see Dr. Orna in the neighborhood walking her little dog, I should ask her? Obviously I will not, because I am a New Yorker and we mind our own business. But still. LW, this is not about this one-time accusation, it’s about the fact that your marriage needs more support! Dealing with mental illness can be incredibly difficult in a relationship, but I don’t think it’s impossible. You two just need to be able to trust each other. And right now you can’t.
Jenée: Yes, please. Dr. Orna and her dog have enough couples to deal with.
Anyway, letter writer, sorry to pass the buck to a therapist here, but it really is the best way forward. Pretend you never heard me mention snooping. I wish you a future with more trust and fewer suspect rashes.

Generally speaking, people with ADHD tend to have trouble sleeping. But new research suggests that sleep problems might not merely be a symptom of the condition but at the root of what’s causing it, reports the Washington Post. A perspective paper (not a clinical trial) in Frontiers in Psychiatry sees a strong correlation between ADHD and people with dysfunctional circadian rhythms, which govern when we sleep and wake. Physician Brandon Luu and co-author Nicholas Fabiano pull together “convergent” evidence that people with ADHD often run on a significantly later internal schedule: up to 78% show delayed sleep timing, with melatonin kicking in much later than is normal.
“In other words, some people with ADHD may not simply be ‘bad at going to bed,'” observes a post at Proactive Psychiatry. “Their internal clock may actually be shifted later.” The researchers urge clinicians to routinely screen for circadian disruption and use sleep tracking as a cheap, low-risk tool for ADHD. The wider field is moving that way, too: Psychiatrists are probing whether misaligned body clocks underlie conditions from depression to schizophrenia, and testing fixes like morning light therapy, structured wake times, and timed exercise to “phase shift” patients closer to society’s demands, notes the Post. The thinking is that in at least some cases, recalibrating the clock could ease the mind.
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Ozempic and Mounjaro can cost an arm and a leg — and maybe a fingernail.
A new study found that people on GLP-1 drugs were nearly 25% more likely to experience a nail disorder than those not on the drugs.
And one particularly squirm-inducing problem was over four times more likely to appear in GLP-1 users.
The new study, presented at the European Academy of Dermatology and Venereology, found that 39% of GLP-1 users reported nail detachment — when the finger or toe nail separates from the nail bed — compared to just 9% of controls.
Once it’s detached, the nail can’t be reattached. It’ll take several months or over a year to regrow.
But that’s not all. Researchers report two thirds of GLP-1 users report at least one nail disorder, including nail discoloration — which appeared 2.7 more frequently in those on the meds.
“Until now, nail changes associated with GLP-1 therapies had essentially been anecdotal,” said study author Charles Taïeb.
Do GLP-1s cause nail problems?
In trials, GLP-1s have shown to cause up to 22% weight loss — while real-world loss is more around 2-8% in a year.
That weight loss can cause nail problems, though, from slower growth to brittle nails. This is connected to nutritional deficiencies as a result of less eating, and dehydration.
Researchers of the new study can’t say for sure whether it’s the meds causing nail issues, or primary effects like weight loss.
While researchers did try to adjust the results accounting for existing dermatological conditions, nutritional deficiencies, and weight loss, nail detachment and discoloration still showed up two to three times as often with GLP-1 users.
“Our findings show a clear association, but they also underline an important point: not everything that happens during GLP-1 treatment is necessarily caused by the treatment itself,” Taïeb said.
Nail and hair loss
A companion study with the same participants in the first showed that hair loss was also significantly higher in those on a GLP-1 drug.
Unusual hair loss (noticeable shedding) was reported by 50% of GLP-1 users compared to 34% in those not on the drug.
Loss in volume or density (overall less hair that remains) was more than twice as common in those on the jab, and scalp redness was around three times as common.
Hair loss on GLP-1s are a known phenomenon. Experts say that it’s “almost always” temporary and a reaction to weight loss and rapid physical changes.
Authors of this study believe that something more than weight loss is at play, though. They note that hair loss was usually accompanied by itching, redness, or scaling — a sign that there’s “an inflammatory component” at play.
“Scalp inflammation was the rule rather than the exception, which clinicians do not currently look for and which may be treatable,” explained author Dr. Bruno Halioua. Doctors can prescribe special shampoos and topical medications to address inflammation on the scalp.
Authors stress these new results should be for “awareness rather than alarm.” Hair and nail loss, at the end of the day, is aesthetic and temporary, while weight loss has a huge long-term impact on many aspects of health.
“These changes are frequent, usually benign, and are not a reason to stop an effective treatment on one’s own initiative,” Halioua said. “Anyone who notices hair shedding, an itchy or red scalp or nail changes should mention it to their doctor rather than discontinue therapy.”

As we recover from a hot week, today’s focus is back on infectious diseases. We’ll start with Covid, one of our most familiar bugs and end with plague, a rare but serious disease. (Spoiler: the risk to you right now is essentially nil.)
Covid-19 bowing out slowly
We’re continuing to see elevated but declining Covid-19 activity across the state. The 2026 peak in wastewater levels was about three weeks ago, which is consistent with last year’s pattern.
We should expect elevated Covid-19 activity for a few weeks. Which matters more in light of the recent arrival of flu.
Flu season under way
On the flu front, transmission rates are increasing day by day. The season took off almost two months ahead of our usual late November timing. This graph shows emergency department visits for Covid-19 are declining as flu increases. You can also see here that RSV, which is the third main respiratory virus we focus on in California, remains flat. It usually increases in late October or November.
I expect in the next couple weeks these top lines will cross, and flu will take its usual role as the main contributor to serious respiratory illness in California through fall and winter.
Combined risk: Because Covid-19 will also remain active for a few weeks, our risk of being exposed to both viruses when we’re out and about is elevated. If you’re at higher risk of severe disease, consider masking up in indoor public spaces.
Flu vaccine uptake: The single most important thing we can do to protect ourselves from the flu is to get the vaccine, and preliminary data show a lot of us know that. Nearly 3 million Californians have already gotten this fall’s flu shot, which is about 400 thousand more than had it by this time last year. So hopefully everyone’s getting the message that it’s game on for flu. Vaccines are available in pharmacies and clinics across the state.
West Nile virus still rising
We’re continuing to see unusually high levels of West Nile virus (WNV) across the state. Remember we’re only infected through mosquito bites, so our risk depends on the burden of the virus in the mosquitoes around us, and our likelihood of getting bitten.
Record warm temperatures through winter, spring, and into summer have supported larger mosquito populations, and also allowed the virus to reproduce more quickly.
Right now we’re at 252 human cases, about five times higher than at this time last year, with 19 deaths.
Almost all parts of the state are impacted. Thirty-eight counties have reported WNV activity, and 23 have human cases. Adjacent Los Angeles and Orange counties have the highest regional burden, with a combined 143 cases and 8 deaths.
There’s no vaccine and no treatment, so it’s mainly about bite prevention.
Remember the four Ds:
Use insect repellent that contains Deet or picaridin.
Cover your arms and legs at dawn and at dusk, when the mosquitoes that carry West Nile are most active.
Drain any standing or stagnant water around your property.
Plague
Finally, plague. You’ve probably seen news about a plague death in a researcher working in a lab in Russia. (To get up to speed, see YLE National’s FAQs from earlier this week.) It’s definitely headline grabbing, but we need more information before knowing what to make of this.
In the meantime it’s a good time to remember what we know about plague. For Californians, plague is not unfamiliar—the bacterial disease is actually endemic to our state. Here’s a refresher.
Is this The Plague? Yes, this is the same bacteria (Yersinia pestis) behind the Black Death that killed about one third of people in medieval Europe. But our situation is very different today.
It’s extremely rare. In 2025, El Dorado County reported a human plague case. The patient was probably infected from a flea bite while camping in South Lake Tahoe. Two people were infected in 2015 after exposure in Yosemite National Park. Nationwide, we see an average of about seven cases per year.
We know how to diagnose and treat it. Antibiotics can treat it, and doctors and nurses in endemic regions are trained to spot and manage it. Untreated, about two in three people with plague die. With treatment, mortality drops to about one in ten.
It usually spreads through fleas after contact with infected rodents, like chipmunks, prairie dogs, mice, rats, or squirrels. Pets, especially cats, can also bring the infection into homes if they roam outdoors. Person to person spread, even in the pneumonic (respiratory) form of the plague (the form the Russian lab worker is suspected to have died from) is very rare. Transmission of plague between people requires prolonged close contact.
It’s regional. In the U.S. plague is found in the rural West, including California, where the bacteria circulates naturally in wild rodents. Urban rats have not been found to carry plague in California.
Note: all cases reported in the East had recently traveled from the West.
Personal note: When I was in the Indian Health Service in Arizona, I took care of a woman with pneumonic plague who was infected by her cat. A smart doc I worked with recognized the signs and started antibiotics right away. She survived, and the source was traced to an infected prairie dog colony near her house.
The California Department of Public Health tests rodents to track plague risk. This map shows where rodents carry antibodies to the bacteria that causes plague—a sign they’ve been exposed.
Back to the Russia case… The most important thing I’m looking for right now out of Russia is any additional cases, because the most concerning scenario is if the bacteria has been modified in a lab toward a more contagious form—which I doubt. If person-to-person contagiousness has changed, then we might see true outbreaks with more cases, and would need to prepare, over time. But that’s theoretical, and not something Californians need to worry about until we know more. I’ll follow this and keep you updated.
Preventing plague in California. Plague prevention is most relevant when we’re in an endemic area doing outdoor activities.
Never touch or feed wild animals.
Keep pets leashed to prevent contact with rodents.
Use insect repellent on socks and clothing to prevent flea bites.
Keep fleas off of your pets by applying flea control products year-round.
Plague exists in our rural areas, but the risk remains extremely low. Keep enjoying our great outdoors (and let me know your great camping spots!), and take simple precautions to stay healthy.
I’ll follow the situation across the sea and provide relevant updates.
Poll: AI and health
I recently joined a Stanford forum on trust and safety in the use of AI in health, and I came away acutely aware that the rapid evolution and adoption of AI is partly a matter of public health. As we navigate where the public health voice belongs in this conversation, I’d love to know what you see as some of the most pressing concerns. Please put any others in the comments.
Bottom line
That’s your roundup for this week! Don’t forget your up-to-date Covid-19 and flu vaccines are in pharmacies and clinics now.
Love,
Matt
Dr. Matt Willis is the author of Your Local Epidemiologist in California. A California native, he’s served as a primary care physician, CDC epidemiologist, and public health officer for Marin County, where he guided the pandemic response. He lives in Marin with his family and their dogs, Teddy and Ramona.