By Dr. Ron Hoffman: Can you really “lose 40 pounds in 40 days”?

If you listen to AM radio, it’s likely you’re continually assailed with ads that claim that you can lose “25-40 pounds in 40 days.” There’s not even a qualifier that this is a best-case scenario like “Results may vary” or the disclaimer “Weight loss may not be typical” (which I thought the Federal Trade Commission used to insist accompany these kinds of pitches).
These incredible successes are said to be achievable with “No shots, no hormones, no surgery.” The advertisers aver that they’re “contractually obligated” to refund your money if you don’t lose all that weight.
What’s the secret sauce, I wonder? The promoters don’t disclose it, but they claim their methods “burn toxic fat” and somehow eliminate your unique personal roadblocks to metabolic efficiency.
They say they use “DNA testing” and some way of pinpointing which of your organs are malfunctioning to individualize your program.
One claim is that a saliva sample of DNA will help match you to your optimal diet. That’s the basis for the emerging science of “nutrigenomics,” but a recent study showed that genetic analysis provided no useful prediction about whether subjects would do better on a low-carb vs. a low-fat diet. Someday the technique may be refined, but I’ve thoroughly field-tested DNA analysis and I’ve concluded that, in its present form, it offers scant useful insights on what or how my patients should be eating.
I’ll confess I have NO idea what the diet centers’ “black box” approach entails. They don’t precisely disclose it. But I do know from talking to patients who’ve participated that it involves a very low calorie diet—as low as 500-600 calories per day.
They say their program is “medically supervised,” but I could find no evidence that they have any health professionals other than a chiropractor on staff. Maybe I’m missing something?
What are the risks of such rapid weight loss?

  • Gallstones, which occur in 12-15% of patients who lose large amounts of weight rapidly
  • Headaches
  • Irritability and depression
  • Fatigue
  • Constipation
  • Hair loss
  • Muscle wasting
  • Dizziness
  • Menstrual irregularities
  • Nutritional deficiencies
  • Heart problems

The latter are particularly disquieting. A recent study revealed that while body fat stores are depleted, paradoxical fat accumulation affects the heart during very low calorie dieting. This was associated with a deterioration in heart function, including the heart’s ability to pump blood. This, along with electrolyte imbalances, might be particularly dangerous for individuals who, by virtue of their obesity, may already be highly predisposed to heart problems.
The good news is that if you survive an eight-week adjustment period, heart function improves, and the circulatory system benefits from reduced weight, lowered lipids, and enhanced insulin sensitivity.
With rapid weight loss, it’s almost impossible to completely spare muscle mass; claims to the contrary that one or the other weight loss scheme uniquely preserves muscle while exclusively burning fat are illusory. Only slow, gradual weight loss supported with resistance training can make it less likely that the dieter will cannibalize their own muscle tissue.
The example of the “Biggest Losers” is instructive. A study was done of contestants after their remarkable diet successes on the program, some achieving 3-digit weight losses with draconian caloric restriction and punishing exercise regimens. All but one or two had regained all the weight that they had lost—and then some. Why was it so difficult for them to maintain their target weight?
National Institutes of Health researchers decided to intensively study these contestants. In a now-famous paper entitled “Persistent metabolic adaptation 6 years after ‘The Biggest Loser’ competition,” scientists discovered that participants had undergone extreme “metabolic adaptation”: their resting metabolic rates—the amount of calories they burned without exertion—had plummeted. This is part of the body’s perverse but evolutionarily-sound adaptation to starvation. When faced with extinction, the body goes into severe conservation mode.
After decades guiding people on weight optimization programs, I’ve concluded that there’s no short-cut around this law of nature. The only way to achieve permanent, sustainable weight loss is via slow gradual weight loss, around 2-4 pounds per month, over a period of 18-36 months.
It’s difficult to sustain because the results aren’t as dramatic, and motivation wanes when you’re looking for a quick fix for your weight woes. Like most things worth doing, it takes time and determination. Holding out the prospect of losing 25-40 pounds in 40 days just doubles down on the duplicity that perpetuates yo-yo dieting.
And we know that losing weight, then regaining it, is worse even than sustained overweight. Yo-yo dieting is associated with a myriad of health woes. It results in a net loss of muscle, which is easily replaced with fat, leading to a higher risk of fatty liver, diabetes and heart disease; worst of all, it discourages dieters from undertaking more permanent, constructive efforts at weight optimization.
There are plenty of better ways to lose weight. Among the more promising:

  • Whole30®️ Diet: I undertook the Whole30 paleo-style diet two and a half years ago as an experiment to improve my energy, focus and athletic performance. While not even intending to, I lost 8-10 pounds of body fat and now fit into size 32 jeans. The Whole30 eliminates all grains, carbs, legumes, sugar, poor quality oils, chips and alcohol. While I “cheat” now and then, it’s still easy to maintain my new weight.
  • Time Restricted Feeding (TRF): Rather than changing what you eat, you simply restrict food intake to a narrower time window. Most poor quality eating occurs at night, so putting aside the feedbag after 6 PM invariably helps you shed pounds.
  • Intermittent Fasting (IF)In the 5:2 plan, you eat normally for five days, then calorie restrict for two; Other schemes, like that of Dr. Valter Longo, incorporate a Fasting Mimicking Diet (FMD) for five days per month.
  • Ketogenic Diet: Drastically restricting carbs yields weight loss dividends, and can be helpful for neurological disorders as well as Type 2 diabetes.
  • Salad and Salmon Diet: A low-carb version of my own Salad and Salmon Diet, incorporating many features of the healthy Mediterranean Diet, has been a mainstay of my approach to weight loss over the years.

If you’re a veteran of the diet wars, I’d love to hear from you—share what’s worked and what hasn’t worked for you. Email me at [email protected] and we’ll discuss on one of our podcasts!


  1. The New England Fat Loss diet says you will lose 20 lbs in the 2 months. You do lose it. You only eat 500 calories a day, basically a starvation diet. It did not last.

  2. Clearly these extreme diet claims are crazy, but if a company has a chiropractor on staff, that could very well constitute medical supervision. Many DCs are well-trained in nutrition. It seems unlikely that a reputable health care provider of any kind would work for a company like that, but there is no essential reason why a chiropractor, especially one trained in functional medicine, could not do such work.

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