How to lose weight sustainably: Kevin Hall on what lasts

To lose weight sustainably, choose a few changes to how you eat and move that you'd be glad to keep for years, build them into the day you actually have, and expect weight to change slowly and then level off. Kevin Hall's research explains why: when weight comes off, appetite rises to pull it back, so whatever change brought the loss has to stay in place to hold it.

Hall describes the usual plan. You make some changes, "some hacks of their metabolism or something like that", for a while, until you reach "some goal weight", and then you relax. "I think that what most people need to realize is that that's not how weight loss works," he told NPR's Life Kit in January 2026. "If you want to maintain the weight that you might end up losing, then you're going to have to incorporate those lifestyle changes permanently into your everyday life" (NPR Life Kit, 2026).

Hall is a nutrition and metabolism scientist who spent 21 years at the NIH studying volunteers in the lab in minute detail (Guardian Science Weekly). He left in 2025 and wrote Food Intelligence with the journalist Julia Belluz, which argues, in its publisher's words, that obesity is "not a result of a failure of will power" (Penguin Random House).

On day one of a new plan, "permanently" can sound bleak. It's also the most useful word in his answer, because it moves the question from how fast you can lose weight to what you'd be willing to keep doing.

What happens when weight comes off?

1. Expect your appetite to push back

Hall describes "two sort of parallel negative feedback circuits": one lowers the energy the body burns, and the other raises appetite. Together they "determine how much weight we lose and where we'll end up plateauing at a lower weight" (Guardian Science Weekly, 5:19). Of the two, he gives appetite the bigger role. "For all of the attention that metabolism gets, I think that the appetite side of things is actually much more important for explaining weight regain and sustainable weight loss" (NPR Life Kit, 2019). People who lose weight, he says, "seem to want to eat even more than they were eating before."

Research points the same way. In one study, 50 adults with overweight or obesity followed a very-low-energy diet for ten weeks. A year later, several of the hormones that signal hunger and fullness, and their own ratings of hunger, still hadn't gone back to where they were before (Sumithran et al., 2011; abstract only). The metabolic side was smaller. In a Norwegian trial, 71 adults with obesity spent eight weeks on a low-calorie diet, and their resting metabolism ended slightly lower than their new size predicted. After four weeks at a steady weight the gap had roughly halved, and it didn't predict who regained a year later (Martins et al., 2020; more in our guide to the weight loss plateau).

In practice, if you're hungrier in the weeks after a few pounds come off, your body is doing what Hall describes. Feed the day: a real first meal and no long gaps. Our guides on always feeling hungry and eating at night show how.

2. Retire the willpower story

Genes don't explain why more people carry extra weight today, though. "Our genes have not changed that much as obesity prevalence has increased over the past 50 years," Hall told the cardiologist Eric Topol. "And so, something in the environment has been driving that" (Ground Truths, 23:05). He thinks the food environment is one of the major drivers.

You can't change your genes or the food industry, but you can change your own small environment: what's in sight, what goes on the plate, what's in your bag when the afternoon gets long. Our guides to portion control and eating at work show how.

How do you choose changes that last?

3. Pick habits you'd keep if the scale didn't move

Yoni Freedhoff, an obesity medicine clinician at the University of Ottawa who runs his own weight-management practice, puts the test in one sentence. "Unless you like the life you're living while you're losing your weight, you're probably not going to keep living that way. And as a consequence, that weight that you've lost will come back" (NPR Life Kit, 2019).

Hall goes further. He likes "to decouple those lifestyle changes that people should think about incorporating and keeping persistent throughout very, very long time periods from focusing on the number on the scale" (NPR Life Kit, 2026).

The diet trials back the point. In a review of 121 trials of 14 popular named diets, most gave modest loss at six months, and "at 12 months the effects on weight reduction ... largely disappear" (Ge et al., 2020). In DIETFITS, 609 adults on a healthy low-fat or low-carb diet lost about the same over a year (Gardner et al., 2018); see our article on the best diet for weight loss.

In practice, run each idea past a three-year test. A plan that bans a food you love is built for a sprint; a version you'd keep might put that food back on a plate, on purpose. If you swing between strict weeks and "I've ruined it" weekends, read our guide to all-or-nothing eating.

4. Stop chasing speed

You'll often hear that weight lost slowly stays off better. In Melbourne, 200 adults with obesity were randomly assigned to lose weight over 12 weeks or over 36 weeks, both aiming at 15% of their weight (Purcell et al., 2014). More of the fast group lost at least 12.5% in the time allowed: 81% against 50%. Those who got close moved on to a maintenance diet, and nearly three years later both groups had regained about 71% of what they'd lost. The rate of loss didn't affect how much came back.

The trial ran inside a supervised hospital program, so it's no case for a crash diet. It says the pace matters less than what you keep doing afterward.

5. Start with two habits, inside your own day

New habits take longer than people expect. In a study of 96 volunteers who each repeated one eating, drinking or activity behavior daily at the same moment, the time for it to feel automatic ranged from 18 to 254 days, and missing one day didn't materially set it back (Lally et al., 2010; abstract only). A later review by the same group puts the average at about 66 days and calls the popular "21 days" a myth (Gardner et al., 2012).

Habit advice has been tested for weight, with modest results. In England, 537 adults with obesity got either usual care from their family doctor's practice or Ten Top Tips, a leaflet of habit-based tips. The leaflet group lost a little more over three months, under a kilo on average, and kept it off for two years, by which time the usual-care group had caught up (Beeken et al., 2017).

So start with one or two habits, each tied to a moment you already have: the snack goes in your bag the night before, dinner goes on a plate before you sit down. Which two depends on where your eating goes off plan: hunger built up over a long day, food in sight, a hard day, or a strict rule that snaps. For the hard days, start with our guide to emotional eating.

How do you keep it?

6. Keep moving, for the keeping

Hall is frustrated that people tie exercise to weight loss: they join a gym, "don't see the scale budge very much", and quit, "which I think is a big mistake". In his view, exercise's "superstar qualities" are "not in the weight loss itself, but the ability to maintain the weight loss over long periods of time." His advice: "Just don't tie the amount of exercise that you're doing to the weight loss" (Guardian Science Weekly, 7:31 to 9:47).

In the National Weight Control Registry, which follows people who lost at least 30 pounds and kept it off for a year, members whose leisure-time activity dropped regained more over ten years (Thomas et al., 2014). That's a link, not proof of cause. Our guide to walking for weight loss covers Herman Pontzer's research on it.

7. Take a weekly look, and count holding steady

Regain is the normal course. Germany's obesity guideline says most people regain 30 to 50% of the weight they lost within the first year, and that longer-term support can improve maintenance or slow regain (German S3 guideline, 2024). In a review of 45 trials with 7,788 adults with obesity who had lost at least 5% of their weight, maintenance programs on both food and activity showed "small but significant benefits" a year later (Dombrowski et al., 2014).

Keeping it off is also possible. In the registry, more than 87% of members were still at least 10% below their highest weight at years five and ten (Thomas et al., 2014). They are self-selected success stories who report their own weight, so they show it can be done, not how often. Members keep a consistent eating pattern across weekdays and weekends, and maintenance may get easier over time (Wing & Phelan, 2005).

So once a week, look at which habits held, and if they slipped, go back to your first two without starting over. For the number itself, Freedhoff offers this:

"A person's best weight is whatever weight they reach when they live the healthiest life they can actually enjoy." Yoni Freedhoff

Start with what you'd keep

Hall's opening point was about the finish line: most plans have one, and the body doesn't. In 2019 he gave the hopeful side. The body "does persistently fight back", he said, but "you can win that battle ... as long as you can enjoy and sustain those behavior changes" (NPR Life Kit, 2019). Today, pick the habit in your current plan that passes the keep-it test, and give it a time. If drinks are part of your evenings, see how to drink less and alcohol and sleep.

To build this around your own day, try the 1h Protocol to Lose Weight Sustainably. Its free first chapter finds the pattern behind the times your eating goes off plan and gives you one thing to do tomorrow. The full program is practical education and takes about an hour: it walks through one day with you, from the first meal to bed, at your own times, and plans for the "just one" moment. You leave with a page of the one or two habits you chose to start, each with a version for harder days, a moment card for your lock screen, a fourteen-day sheet, and days seven and fourteen in your calendar. You can write your own goal, a weight goal included; the program never sets a target, calories or a diet. Four one-tap check-ins follow by email on days 1, 7, 14 and 30. The program isn't for anyone who is pregnant or breastfeeding, or living with an eating disorder, now or in the past. Start free

Frequently asked questions

How do I lose weight sustainably?

Pick one or two changes to how you eat and move that you'd keep for years, tie each to a moment in your day, and keep them after the weight comes off. Appetite rises after weight loss, so in Kevin Hall's view the changes have to become permanent (NPR Life Kit, 2026).

Can you lose weight without dieting?

Yes, through habits, though expect it to be slow. No named diet has beaten the others over a year (Ge et al., 2020), and in an English trial a leaflet of habit tips led to a little more loss than usual care, kept for two years (Beeken et al., 2017).

Is slow weight loss more sustainable than fast?

Not in the trial that tested it. Adults with obesity who lost weight over 12 weeks or over 36 weeks regained about the same share, roughly 71%, after nearly three years (Purcell et al., 2014). What you keep doing afterward matters more than the pace.

How long does it take to lose weight sustainably?

No one can honestly give you a date. Weight usually changes slowly and then levels off, and habits take time too: in one study, 18 to 254 days to feel automatic (Lally et al., 2010). Holding a lower weight steady is a real result.

How do I find motivation to keep going?

Judge your days by whether the habits happened, since the scale moves slowly and unevenly. Hall warns that people who don't see the scale move may give up on exercise that is helping them (Guardian Science Weekly, 8:36). Write down your reason in your own words, and see our guide on how to get motivated. If eating still feels out of your control after two weeks, talk to someone you trust.

Sources

This article draws on Kevin Hall's interviews on NPR's Life Kit, Guardian Science Weekly and Ground Truths, Yoni Freedhoff's interview on Life Kit, the publisher's description of Hall's book, and the studies and guideline listed below.

• The science of losing weight (podcast episode with Kevin Hall, NPR Life Kit, 2026)
• The real science of weight loss with the US's leading nutritional scientist (podcast episode with Kevin Hall, Guardian Science Weekly, 2025)
• The biology of weight loss (podcast episode with Kevin Hall and Holly Wyatt, NPR Life Kit, 2019)
• Kevin Hall: What should we eat? (podcast episode, Ground Truths with Eric Topol, 2024)
• Julia Belluz and Kevin Hall, Food Intelligence (book, publisher page, 2025)
• A saner mindset for weight loss (podcast episode with Yoni Freedhoff, NPR Life Kit, 2019)
• Sumithran et al, Long-term persistence of hormonal adaptations to weight loss (study of 50 adults with overweight or obesity, abstract only, 2011)
• Martins et al, Metabolic adaptation is an illusion, only present when participants are in negative energy balance (analysis of a trial with 71 adults with obesity in Norway, 2020)
• Purcell et al, The effect of rate of weight loss on long-term weight management (randomized trial, 200 adults with obesity in Australia, abstract only, 2014)
• Ge et al, Comparison of dietary macronutrient patterns of 14 popular named dietary programmes (systematic review and network meta-analysis of 121 trials, 2020)
• Gardner et al, Effect of low-fat vs low-carbohydrate diet on 12-month weight loss: the DIETFITS randomized clinical trial (randomized trial, 609 adults, 2018)
• Lally et al, How are habits formed: modelling habit formation in the real world (study of 96 volunteers, abstract only, 2010)
• Gardner, Lally & Wardle, Making health habitual (review for family doctors, 2012)
• Beeken et al, A brief intervention for weight control based on habit-formation theory delivered through primary care (randomized trial, 537 adults with obesity in England, 2017)
• Dombrowski et al, Long term maintenance of weight loss with non-surgical interventions in obese adults (systematic review and meta-analyses of 45 trials, 2014)
• German Obesity Society et al, S3 guideline on the prevention and treatment of obesity, version 5.0 (national guideline, in German, 2024)
• Thomas et al, Weight-loss maintenance for 10 years in the National Weight Control Registry (registry study of 2,886 members, self-reported, abstract only, 2014)
• Wing & Phelan, Long-term weight loss maintenance (review of the registry, 2005)