My idea of exercise is bicycling to the ice-cream parlor. I view abbreviations like “abs” and “carbs” as contortions of the lexicon by people who would have the temerity to suggest that chocolate isn’t good for me. But if at first I found the idea of a week at a famously low-key health spa about as appealing as a slice of tofu pizza, I am old enough to realize that I have been spending perhaps too much time with my friends Baskin and Robbins. When it comes to spas, Rancho la Puerta in Baja, Calif., is the real deal. One of its cofounders, Edmund Szekely, was part of a French scientific mission in the late 1930s that roamed the globe to document the effects of climate on health. Convinced that the enviably moderate weather of San Diego and tiny Tecate, Mexico, just 45 minutes east of it, was the world’s finest – and not exactly eager to race back to France at that particular point in history – he established Rancho la Puerta in 1940 with his wife, Deborah. Mrs. Szekely, now 83 and a lodestar in the fitness firmament, still plays an active role in the life of the ranch. Her domain is a vast one, stretching over 575 acres at the foot of Mount Kuchumaa, which straddles the California-Mexico border. Virgin stands of oak trees alternate with lushly landscaped gardens that provide an Edenic counterpoint to the chaparral-covered hills all around. Paved paths connect various fitness and health buildings with the cottages and villa suites that serve as accommodation for up to 150 guests weekly. I found the most intriguing aspect of the place to be on the one hand the inevitability of getting lost and on the other the certainty of ending up at a pavilion where an activity demanding temporary suspension of decadent dietary ways and, very probably, physical exertion was in progress.

Which may well be the point. You have to walk to classes, generally 45 minutes long, where fitness gurus encourage you to walk more, stretch more, or eat better. Although the spa offers only one package, a week-long all-inclusive that runs from Saturday to Saturday, there is freedom to choose from up to 80 activities during that timeframe: early morning hike and exercise programs, Pilates and yoga workshops, Afro-Latin and salsa dancing classes, cardio-boxing, arts and crafts, bird walks…no one can do it all, or is expected to.

For anyone who has ever wanted to take a cruise but shies away from the water, I have a proposition: spend a week down at the ranch. The place is so big, the activities so numerous, and the avenues of escape so limited – slipping into Tecate for a taco is not really an option – the net effect is like being on a land cruise.

That away-at-sea feeling extends to the dining experience, which is fairly communal given the one principal dining hall. Vegetarian dishes take center stage, with plenty of greens, legumes, whole grains, and other fibers – lots of fibers – little fat or salt (but help yourself to the Vegit), and no white flour or refined sugar. Arriving as I had after spending the summer in Paris, a city impervious to carbohydrate reform, all this theoretically good stuff was literally a shock to my sys tem. I discovered that in the space of two days my metabolism had actually accelerated to the point where I had to dip into my secret supply of Hostess Powdered Donettes, guiltily purchased at a gas station on the other side of the border prior to my arrival, to slow it down.

By Day Three the stash was gone, and I found myself freefalling into a strange new world of unmatched regularity and freedom, if only short-term, from sugar dependency. The problem was that I was already losing weight – I could feel it – but I didn’t really want to. I am preternaturally thin and gorgeous (just ask my mother). But if one of my gym-bound friend’s admirable goals of being “a god at the beach” will be forever beyond my reach, I did consider toning a viable aspiration. Could I replace my rapidly diminishing fat with at least a hint of muscle?

I decided to try by hooking up with the men’s fitness program. Most of the fitness classes and all the hikes at Rancho la Puerta are designed for both sexes, but perhaps in deference to the number of men who now take spa vacations, there are a few offerings just for the guys. The fact that, unbeknownst to me, it was Mother-Daughter week at the ranch when I was there meant that the men’s classes weren’t terribly crowded. As the week is progressive – start off slow, build up your endurance – and I view free weights as faceless enemies, I opted for the “Strength Training without Weights” course. On Day One I discovered with horror that I could no longer do push-ups. On Day Two I managed six. By Day Three, Raymond, the Belgian fitness instructor, convinced me that it is possible to inflict great pain on one’s own body in the complete absence of weights.

I gathered that all this exertion was somehow good for me – like C-SPAN for my body – but I was more sore than sure, so I signed up for a Golden Door Classic Massage (Ms. Szekely also founded the Golden Door Spa in Escondido, Calif.).The new and immaculately clean Vilas Health Center offers a whole range of indulgent spa treats and treatments: Hot Stone massages, salt glows, herbal wraps, facials. These are welcome complements to the more rigorous fitness activities that are really the cornerstone of life at the ranch.

Foremost among which are the hikes. The natural setting of Rancho la Puerta and the 3,000 rolling acres around it are aesthetic detox for over urbanized drones like me, and the spa staff knows it. Early morning, when most of the hillside rambles take place, is the best time to savor the fresh air when it’s still redolent of sagebrush and oak, and not too hot. The one I didn’t want to miss was the Organic Vegetable Garden Breakfast Hike, a four-mile, two-and-a-half hour walk to the organic gardens that supply much of the ranch’s food. The lure? The prospect of a full breakfast with a few of the ingredients verboten elsewhere on the premises. The catch was that the hike departed at 6:15 a.m., and I didn’t show up until close to 6:30 a.m. But I would not be deterred – especially with a rumor of homemade chocolate carrot cake in the air. I sprinted to the main office and hitched a ride on the ranch van. The breakfast cake was very good indeed and definitely worth faking my ascent to be able to get to it first.

I did join the return leg of the hike, however, and it was during the walk back along the base of Mount Kuchumaa that I began to understand more fully the secret of the spa’s success. There I was with fellow spa-goers from all over the country, coaxed out of bed (I assumed) by the faint promise of a bit of chocolate with their breakfast (but try not to enunciate the word, please).

Given the absence of traffic or artificial time constraints, it is all but impossible not to be moved by the natural setting, and unnatural to not strike up a conversation with whomever happens to be tramping alongside you. I had already had the good fortune to meet Esther Coopersmith, Democratic Party doyenne of Washington, D.C., at one dinner, but on the breakfast hike I met a pretty girl from Montreal who, once her mother let her out of her sight for two seconds, told me she helped produce a documentary on global warming that appears on the DVD for “The Day After Tomorrow.” There were even a few soft-spoken New Yorkers.

All this, I concluded, was less about fitness than a recalibration of one’s reflexes. Shouldn’t strolling among the oak groves and chatting with fellow travelers be the norm, and reaching for the remote control and a Diet Coke the aberration? It may take a week’s dose of discipline and a dash of renunciation to arrive at a healthier outlook on life, but the journey is unquestionably worth taking.